diff --git a/backend/app.py b/backend/app.py
index 6211fd1..1983754 100644
--- a/backend/app.py
+++ b/backend/app.py
@@ -1,6 +1,6 @@
 """
 SchoolCompare.co.uk API
-Serves primary school (KS2) performance data for comparing schools.
+Serves primary and secondary school performance data for comparing schools.
 Uses real data from UK Government Compare School Performance downloads.
 """
 
@@ -151,7 +151,7 @@ async def lifespan(app: FastAPI):
 
 app = FastAPI(
     title="SchoolCompare API",
-    description="API for comparing primary school (KS2) performance data - schoolcompare.co.uk",
+    description="API for comparing primary and secondary school performance data - schoolcompare.co.uk",
     version="2.0.0",
     lifespan=lifespan,
     # Disable docs in production for security
@@ -213,21 +213,23 @@ async def get_schools(
         None, description="Filter by local authority", max_length=100
     ),
     school_type: Optional[str] = Query(None, description="Filter by school type", max_length=100),
+    phase: Optional[str] = Query(None, description="Filter by phase: primary, secondary, all-through", max_length=50),
     postcode: Optional[str] = Query(None, description="Search near postcode", max_length=10),
     radius: float = Query(5.0, ge=0.1, le=50, description="Search radius in miles"),
     page: int = Query(1, ge=1, le=1000, description="Page number"),
     page_size: int = Query(None, ge=1, le=100, description="Results per page"),
 ):
     """
-    Get list of unique primary schools with pagination.
+    Get list of schools with pagination.
 
     Returns paginated results with total count for efficient loading.
-    Supports location-based search using postcode.
+    Supports location-based search using postcode and phase filtering.
     """
     # Sanitize inputs
     search = sanitize_search_input(search)
     local_authority = sanitize_search_input(local_authority)
     school_type = sanitize_search_input(school_type)
+    phase = sanitize_search_input(phase)
     postcode = validate_postcode(postcode)
 
     df = load_school_data()
@@ -253,9 +255,25 @@ async def get_schools(
         )
         df_latest = df_latest.merge(prev_rwm, on="urn", how="left")
 
+    # Phase filter
+    if phase:
+        phase_lower = phase.lower()
+        if phase_lower in ("primary", "secondary", "all-through", "all_through"):
+            # Map param values to GIAS phase strings (partial match)
+            phase_map = {
+                "primary": "primary",
+                "secondary": "secondary",
+                "all-through": "all-through",
+                "all_through": "all-through",
+            }
+            phase_substr = phase_map[phase_lower]
+            schools_df_phase_mask = df_latest["phase"].str.lower().str.contains(phase_substr, na=False)
+            df_latest = df_latest[schools_df_phase_mask]
+
     # Include key result metrics for display on cards
     location_cols = ["latitude", "longitude"]
     result_cols = [
+        "phase",
         "year",
         "rwm_expected_pct",
         "rwm_high_pct",
@@ -264,6 +282,8 @@ async def get_schools(
         "writing_expected_pct",
         "maths_expected_pct",
         "total_pupils",
+        "attainment_8_score",
+        "english_maths_standard_pass_pct",
     ]
     available_cols = [
         c
@@ -364,7 +384,7 @@ async def get_schools(
 @app.get("/api/schools/{urn}")
 @limiter.limit(f"{settings.rate_limit_per_minute}/minute")
 async def get_school_details(request: Request, urn: int):
-    """Get detailed KS2 data for a specific primary school across all years."""
+    """Get detailed performance data for a specific school across all years."""
     # Validate URN range (UK school URNs are 6 digits)
     if not (100000 <= urn <= 999999):
         raise HTTPException(status_code=400, detail="Invalid URN format")
@@ -406,7 +426,7 @@ async def get_school_details(request: Request, urn: int):
             "age_range": latest.get("age_range", ""),
             "latitude": latest.get("latitude"),
             "longitude": latest.get("longitude"),
-            "phase": "Primary",
+            "phase": latest.get("phase"),
             # GIAS fields
             "website": latest.get("website"),
             "headteacher_name": latest.get("headteacher_name"),
@@ -433,7 +453,7 @@ async def compare_schools(
     request: Request,
     urns: str = Query(..., description="Comma-separated URNs", max_length=100)
 ):
-    """Compare multiple primary schools side by side."""
+    """Compare multiple schools side by side."""
     df = load_school_data()
 
     if df.empty:
@@ -487,10 +507,66 @@ async def get_filter_options(request: Request):
             "years": [],
         }
 
+    # Phases: return values from data, ordered sensibly
+    phases = sorted(df["phase"].dropna().unique().tolist()) if "phase" in df.columns else []
+
     return {
         "local_authorities": sorted(df["local_authority"].dropna().unique().tolist()),
         "school_types": sorted(df["school_type"].dropna().unique().tolist()),
         "years": sorted(df["year"].dropna().unique().tolist()),
+        "phases": phases,
+    }
+
+
+@app.get("/api/national-averages")
+@limiter.limit(f"{settings.rate_limit_per_minute}/minute")
+async def get_national_averages(request: Request):
+    """
+    Compute national average for each metric from the latest data year.
+    Returns separate averages for primary (KS2) and secondary (KS4) schools.
+    Values are derived from the loaded DataFrame so they automatically
+    stay current when new data is loaded.
+    """
+    df = load_school_data()
+    if df.empty:
+        return {"primary": {}, "secondary": {}}
+
+    latest_year = int(df["year"].max())
+    df_latest = df[df["year"] == latest_year]
+
+    ks2_metrics = [
+        "rwm_expected_pct", "rwm_high_pct",
+        "reading_expected_pct", "writing_expected_pct", "maths_expected_pct",
+        "reading_avg_score", "maths_avg_score", "gps_avg_score",
+        "reading_progress", "writing_progress", "maths_progress",
+        "overall_absence_pct", "persistent_absence_pct",
+        "disadvantaged_gap", "disadvantaged_pct", "sen_support_pct",
+    ]
+    ks4_metrics = [
+        "attainment_8_score", "progress_8_score",
+        "english_maths_standard_pass_pct", "english_maths_strong_pass_pct",
+        "ebacc_entry_pct", "ebacc_standard_pass_pct", "ebacc_strong_pass_pct",
+        "ebacc_avg_score", "gcse_grade_91_pct",
+    ]
+
+    def _means(sub_df, metric_list):
+        out = {}
+        for col in metric_list:
+            if col in sub_df.columns:
+                val = sub_df[col].dropna()
+                if len(val) > 0:
+                    out[col] = round(float(val.mean()), 2)
+        return out
+
+    # Primary: schools where KS2 data is non-null
+    primary_df = df_latest[df_latest["rwm_expected_pct"].notna()]
+    # Secondary: schools where KS4 data is non-null
+    secondary_df = df_latest[df_latest["attainment_8_score"].notna()]
+
+    return {
+        "year": latest_year,
+        "primary": _means(primary_df, ks2_metrics),
+        "secondary": _means(secondary_df, ks4_metrics),
     }
 
 
@@ -498,7 +574,7 @@ async def get_filter_options(request: Request):
 @limiter.limit(f"{settings.rate_limit_per_minute}/minute")
 async def get_available_metrics(request: Request):
     """
-    Get list of available KS2 performance metrics for primary schools.
+    Get list of available performance metrics for schools.
 
     This is the single source of truth for metric definitions.
     Frontend should consume this to avoid duplication.
@@ -517,7 +593,7 @@ async def get_available_metrics(request: Request):
 @limiter.limit(f"{settings.rate_limit_per_minute}/minute")
 async def get_rankings(
     request: Request,
-    metric: str = Query("rwm_expected_pct", description="KS2 metric to rank by", max_length=50),
+    metric: str = Query("rwm_expected_pct", description="Metric to rank by", max_length=50),
     year: Optional[int] = Query(
         None, description="Specific year (defaults to most recent)", ge=2000, le=2100
     ),
@@ -526,7 +602,7 @@ async def get_rankings(
         None, description="Filter by local authority", max_length=100
     ),
 ):
-    """Get primary school rankings by a specific KS2 metric."""
+    """Get school rankings by a specific metric."""
     # Sanitize local authority input
     local_authority = sanitize_search_input(local_authority)
 
diff --git a/backend/data_loader.py b/backend/data_loader.py
index 26aa79a..95e1dd4 100644
--- a/backend/data_loader.py
+++ b/backend/data_loader.py
@@ -113,6 +113,7 @@ def haversine_distance(lat1: float, lon1: float, lat2: float, lon2: float) -> fl
 # =============================================================================
 
 _MAIN_QUERY = text("""
+    -- Branch 1: Primary schools (KS2 data; KS4 columns NULL)
     SELECT
         s.urn,
         s.school_name,
@@ -137,11 +138,11 @@ _MAIN_QUERY = text("""
         l.postcode,
         l.latitude,
         l.longitude,
-        -- KS2 performance
         k.year,
         k.source_urn,
         k.total_pupils,
         k.eligible_pupils,
+        -- KS2 columns
         k.rwm_expected_pct,
         k.rwm_high_pct,
         k.reading_expected_pct,
@@ -175,11 +176,116 @@ _MAIN_QUERY = text("""
         k.eal_pct,
         k.sen_support_pct,
         k.sen_ehcp_pct,
-        k.stability_pct
+        k.stability_pct,
+        -- KS4 columns (NULL for primary)
+        NULL::numeric AS attainment_8_score,
+        NULL::numeric AS progress_8_score,
+        NULL::numeric AS progress_8_lower_ci,
+        NULL::numeric AS progress_8_upper_ci,
+        NULL::numeric AS progress_8_english,
+        NULL::numeric AS progress_8_maths,
+        NULL::numeric AS progress_8_ebacc,
+        NULL::numeric AS progress_8_open,
+        NULL::numeric AS english_maths_strong_pass_pct,
+        NULL::numeric AS english_maths_standard_pass_pct,
+        NULL::numeric AS ebacc_entry_pct,
+        NULL::numeric AS ebacc_strong_pass_pct,
+        NULL::numeric AS ebacc_standard_pass_pct,
+        NULL::numeric AS ebacc_avg_score,
+        NULL::numeric AS gcse_grade_91_pct,
+        NULL::numeric AS prior_attainment_avg
     FROM marts.dim_school s
     JOIN marts.dim_location l ON s.urn = l.urn
     JOIN marts.fact_ks2_performance k ON s.urn = k.urn
-    ORDER BY s.school_name, k.year
+
+    UNION ALL
+
+    -- Branch 2: Secondary schools (KS4 data; KS2 columns NULL)
+    SELECT
+        s.urn,
+        s.school_name,
+        s.phase,
+        s.school_type,
+        s.academy_trust_name   AS trust_name,
+        s.academy_trust_uid    AS trust_uid,
+        s.religious_character  AS religious_denomination,
+        s.gender,
+        s.age_range,
+        s.capacity,
+        s.headteacher_name,
+        s.website,
+        s.ofsted_grade,
+        s.ofsted_date,
+        s.ofsted_framework,
+        l.local_authority_name AS local_authority,
+        l.local_authority_code,
+        l.address_line1        AS address1,
+        l.address_line2        AS address2,
+        l.town,
+        l.postcode,
+        l.latitude,
+        l.longitude,
+        k4.year,
+        k4.source_urn,
+        k4.total_pupils,
+        k4.eligible_pupils,
+        -- KS2 columns (NULL for secondary)
+        NULL::numeric AS rwm_expected_pct,
+        NULL::numeric AS rwm_high_pct,
+        NULL::numeric AS reading_expected_pct,
+        NULL::numeric AS reading_high_pct,
+        NULL::numeric AS reading_avg_score,
+        NULL::numeric AS reading_progress,
+        NULL::numeric AS writing_expected_pct,
+        NULL::numeric AS writing_high_pct,
+        NULL::numeric AS writing_progress,
+        NULL::numeric AS maths_expected_pct,
+        NULL::numeric AS maths_high_pct,
+        NULL::numeric AS maths_avg_score,
+        NULL::numeric AS maths_progress,
+        NULL::numeric AS gps_expected_pct,
+        NULL::numeric AS gps_high_pct,
+        NULL::numeric AS gps_avg_score,
+        NULL::numeric AS science_expected_pct,
+        NULL::numeric AS reading_absence_pct,
+        NULL::numeric AS writing_absence_pct,
+        NULL::numeric AS maths_absence_pct,
+        NULL::numeric AS gps_absence_pct,
+        NULL::numeric AS science_absence_pct,
+        NULL::numeric AS rwm_expected_boys_pct,
+        NULL::numeric AS rwm_high_boys_pct,
+        NULL::numeric AS rwm_expected_girls_pct,
+        NULL::numeric AS rwm_high_girls_pct,
+        NULL::numeric AS rwm_expected_disadvantaged_pct,
+        NULL::numeric AS rwm_expected_non_disadvantaged_pct,
+        NULL::numeric AS disadvantaged_gap,
+        NULL::numeric AS disadvantaged_pct,
+        NULL::numeric AS eal_pct,
+        k4.sen_support_pct,
+        k4.sen_ehcp_pct,
+        NULL::numeric AS stability_pct,
+        -- KS4 columns
+        k4.attainment_8_score,
+        k4.progress_8_score,
+        k4.progress_8_lower_ci,
+        k4.progress_8_upper_ci,
+        k4.progress_8_english,
+        k4.progress_8_maths,
+        k4.progress_8_ebacc,
+        k4.progress_8_open,
+        k4.english_maths_strong_pass_pct,
+        k4.english_maths_standard_pass_pct,
+        k4.ebacc_entry_pct,
+        k4.ebacc_strong_pass_pct,
+        k4.ebacc_standard_pass_pct,
+        k4.ebacc_avg_score,
+        k4.gcse_grade_91_pct,
+        k4.prior_attainment_avg
+    FROM marts.dim_school s
+    JOIN marts.dim_location l ON s.urn = l.urn
+    JOIN marts.fact_ks4_performance k4 ON s.urn = k4.urn
+
+    ORDER BY school_name, year
 """)
 
 
diff --git a/backend/schemas.py b/backend/schemas.py
index fbbdae0..b3e0f0d 100644
--- a/backend/schemas.py
+++ b/backend/schemas.py
@@ -401,6 +401,70 @@ METRIC_DEFINITIONS = {
         "type": "score",
         "category": "trends",
     },
+    # ── GCSE Performance (KS4) ────────────────────────────────────────────
+    "attainment_8_score": {
+        "name": "Attainment 8",
+        "short_name": "Att 8",
+        "description": "Average grade across a pupil's best 8 GCSEs including English and Maths",
+        "type": "score",
+        "category": "gcse",
+    },
+    "progress_8_score": {
+        "name": "Progress 8",
+        "short_name": "P8",
+        "description": "Progress from KS2 baseline to GCSE relative to similar pupils nationally (0 = national average)",
+        "type": "score",
+        "category": "gcse",
+    },
+    "english_maths_standard_pass_pct": {
+        "name": "English & Maths Grade 4+",
+        "short_name": "E&M 4+",
+        "description": "% of pupils achieving grade 4 (standard pass) or above in both English and Maths",
+        "type": "percentage",
+        "category": "gcse",
+    },
+    "english_maths_strong_pass_pct": {
+        "name": "English & Maths Grade 5+",
+        "short_name": "E&M 5+",
+        "description": "% of pupils achieving grade 5 (strong pass) or above in both English and Maths",
+        "type": "percentage",
+        "category": "gcse",
+    },
+    "ebacc_entry_pct": {
+        "name": "EBacc Entry %",
+        "short_name": "EBacc Entry",
+        "description": "% of pupils entered for the English Baccalaureate (English, Maths, Sciences, Languages, Humanities)",
+        "type": "percentage",
+        "category": "gcse",
+    },
+    "ebacc_standard_pass_pct": {
+        "name": "EBacc Grade 4+",
+        "short_name": "EBacc 4+",
+        "description": "% of pupils achieving grade 4+ across all EBacc subjects",
+        "type": "percentage",
+        "category": "gcse",
+    },
+    "ebacc_strong_pass_pct": {
+        "name": "EBacc Grade 5+",
+        "short_name": "EBacc 5+",
+        "description": "% of pupils achieving grade 5+ across all EBacc subjects",
+        "type": "percentage",
+        "category": "gcse",
+    },
+    "ebacc_avg_score": {
+        "name": "EBacc Average Score",
+        "short_name": "EBacc Avg",
+        "description": "Average points score across EBacc subjects",
+        "type": "score",
+        "category": "gcse",
+    },
+    "gcse_grade_91_pct": {
+        "name": "GCSE Grade 9–1 %",
+        "short_name": "GCSE 9–1",
+        "description": "% of GCSE entries achieving a grade 9 to 1",
+        "type": "percentage",
+        "category": "gcse",
+    },
 }
 
 # Ranking columns to include in rankings response
@@ -456,6 +520,16 @@ RANKING_COLUMNS = [
     "rwm_expected_3yr_pct",
     "reading_avg_3yr",
     "maths_avg_3yr",
+    # GCSE (KS4)
+    "attainment_8_score",
+    "progress_8_score",
+    "english_maths_standard_pass_pct",
+    "english_maths_strong_pass_pct",
+    "ebacc_entry_pct",
+    "ebacc_standard_pass_pct",
+    "ebacc_strong_pass_pct",
+    "ebacc_avg_score",
+    "gcse_grade_91_pct",
 ]
 
 # School listing columns
diff --git a/nextjs-app/app/layout.tsx b/nextjs-app/app/layout.tsx
index 7ba5770..f43e8d3 100644
--- a/nextjs-app/app/layout.tsx
+++ b/nextjs-app/app/layout.tsx
@@ -23,11 +23,11 @@ const playfairDisplay = Playfair_Display({
 
 export const metadata: Metadata = {
   title: {
-    default: 'SchoolCompare | Compare Primary School Performance',
+    default: 'SchoolCompare | Compare School Performance',
     template: '%s | SchoolCompare',
   },
-  description: 'Compare primary school KS2 performance across England',
-  keywords: 'school comparison, KS2 results, primary school performance, England schools, SATs results',
+  description: 'Compare primary and secondary school SATs and GCSE performance across England',
+  keywords: 'school comparison, KS2 results, KS4 results, primary school, secondary school, England schools, SATs results, GCSE results',
   authors: [{ name: 'SchoolCompare' }],
   manifest: '/manifest.json',
   icons: {
@@ -37,15 +37,15 @@ export const metadata: Metadata = {
   },
   openGraph: {
     type: 'website',
-    title: 'SchoolCompare | Compare Primary School Performance',
-    description: 'Compare primary school KS2 performance across England',
+    title: 'SchoolCompare | Compare School Performance',
+    description: 'Compare primary and secondary school SATs and GCSE performance across England',
     url: 'https://schoolcompare.co.uk',
     siteName: 'SchoolCompare',
   },
   twitter: {
     card: 'summary',
-    title: 'SchoolCompare | Compare Primary School Performance',
-    description: 'Compare primary school KS2 performance across England',
+    title: 'SchoolCompare | Compare School Performance',
+    description: 'Compare primary and secondary school SATs and GCSE performance across England',
   },
 };
 
diff --git a/nextjs-app/app/page.tsx b/nextjs-app/app/page.tsx
index 0f6d083..56d3206 100644
--- a/nextjs-app/app/page.tsx
+++ b/nextjs-app/app/page.tsx
@@ -11,6 +11,7 @@ interface HomePageProps {
     search?: string;
     local_authority?: string;
     school_type?: string;
+    phase?: string;
     page?: string;
     postcode?: string;
     radius?: string;
@@ -19,7 +20,7 @@ interface HomePageProps {
 
 export const metadata = {
   title: 'Home',
-  description: 'Search and compare primary school KS2 performance across England',
+  description: 'Search and compare school performance across England',
 };
 
 // Force dynamic rendering (no static generation at build time)
@@ -38,6 +39,7 @@ export default async function HomePage({ searchParams }: HomePageProps) {
     params.search ||
     params.local_authority ||
     params.school_type ||
+    params.phase ||
     params.postcode
   );
 
@@ -52,6 +54,7 @@ export default async function HomePage({ searchParams }: HomePageProps) {
         search: params.search,
         local_authority: params.local_authority,
         school_type: params.school_type,
+        phase: params.phase,
         postcode: params.postcode,
         radius,
         page,
@@ -65,7 +68,7 @@ export default async function HomePage({ searchParams }: HomePageProps) {
     return (
       <HomeView
         initialSchools={schoolsData}
-        filters={filtersData || { local_authorities: [], school_types: [], years: [] }}
+        filters={filtersData || { local_authorities: [], school_types: [], years: [], phases: [] }}
         totalSchools={dataInfo?.total_schools ?? null}
       />
     );
@@ -76,7 +79,7 @@ export default async function HomePage({ searchParams }: HomePageProps) {
     return (
       <HomeView
         initialSchools={{ schools: [], page: 1, page_size: 50, total: 0, total_pages: 0 }}
-        filters={{ local_authorities: [], school_types: [], years: [] }}
+        filters={{ local_authorities: [], school_types: [], years: [], phases: [] }}
         totalSchools={null}
       />
     );
diff --git a/nextjs-app/app/rankings/page.tsx b/nextjs-app/app/rankings/page.tsx
index 57a547f..1379735 100644
--- a/nextjs-app/app/rankings/page.tsx
+++ b/nextjs-app/app/rankings/page.tsx
@@ -17,8 +17,8 @@ interface RankingsPageProps {
 
 export const metadata: Metadata = {
   title: 'School Rankings',
-  description: 'Top-ranked primary schools by KS2 performance across England',
-  keywords: 'school rankings, top schools, best schools, KS2 rankings, school league tables',
+  description: 'Top-ranked schools by SATs and GCSE performance across England',
+  keywords: 'school rankings, top schools, best schools, KS2 rankings, KS4 rankings, school league tables',
 };
 
 // Force dynamic rendering
diff --git a/nextjs-app/components/FilterBar.tsx b/nextjs-app/components/FilterBar.tsx
index 401525e..9dc25b5 100644
--- a/nextjs-app/components/FilterBar.tsx
+++ b/nextjs-app/components/FilterBar.tsx
@@ -27,6 +27,7 @@ export function FilterBar({ filters, isHero }: FilterBarProps) {
 
   const currentLA = searchParams.get('local_authority') || '';
   const currentType = searchParams.get('school_type') || '';
+  const currentPhase = searchParams.get('phase') || '';
 
   useEffect(() => {
     const handleKeyDown = (e: KeyboardEvent) => {
@@ -86,7 +87,7 @@ export function FilterBar({ filters, isHero }: FilterBarProps) {
     });
   };
 
-  const hasActiveFilters = currentSearch || currentLA || currentType || currentPostcode;
+  const hasActiveFilters = currentSearch || currentLA || currentType || currentPhase || currentPostcode;
 
   return (
     <div className={`${styles.filterBar} ${isPending ? styles.isLoading : ''} ${isHero ? styles.heroMode : ''}`}>
@@ -152,6 +153,22 @@ export function FilterBar({ filters, isHero }: FilterBarProps) {
           ))}
         </select>
 
+        {filters.phases && filters.phases.length > 0 && (
+          <select
+            value={currentPhase}
+            onChange={(e) => handleFilterChange('phase', e.target.value)}
+            className={styles.filterSelect}
+            disabled={isPending}
+          >
+            <option value="">All Phases</option>
+            {filters.phases.map((p) => (
+              <option key={p} value={p.toLowerCase()}>
+                {p}
+              </option>
+            ))}
+          </select>
+        )}
+
         {hasActiveFilters && (
           <button onClick={handleClearFilters} className={`btn btn-tertiary ${styles.clearButton}`} type="button" disabled={isPending}>
             Clear Filters
diff --git a/nextjs-app/components/Footer.tsx b/nextjs-app/components/Footer.tsx
index 666cad6..54d1bac 100644
--- a/nextjs-app/components/Footer.tsx
+++ b/nextjs-app/components/Footer.tsx
@@ -15,7 +15,7 @@ export function Footer() {
           <div className={styles.section}>
             <h3 className={styles.title}>SchoolCompare</h3>
             <p className={styles.description}>
-              Compare primary schools across England.
+              Compare primary and secondary schools across England.
             </p>
           </div>
 
diff --git a/nextjs-app/components/HomeView.tsx b/nextjs-app/components/HomeView.tsx
index 5166e73..baffd81 100644
--- a/nextjs-app/components/HomeView.tsx
+++ b/nextjs-app/components/HomeView.tsx
@@ -51,8 +51,8 @@ export function HomeView({ initialSchools, filters, totalSchools }: HomeViewProp
       {/* Combined Hero + Search and Filters */}
       {!isSearchActive && (
         <div className={styles.heroSection}>
-          <h1 className={styles.heroTitle}>Compare Primary School Performance</h1>
-          <p className={styles.heroDescription}>Search and compare KS2 results for thousands of schools across England</p>
+          <h1 className={styles.heroTitle}>Compare School Performance</h1>
+          <p className={styles.heroDescription}>Search and compare SATs and GCSE results for thousands of schools across England</p>
         </div>
       )}
 
@@ -64,7 +64,7 @@ export function HomeView({ initialSchools, filters, totalSchools }: HomeViewProp
       {/* Discovery section shown on landing page before any search */}
       {!isSearchActive && initialSchools.schools.length === 0 && (
         <div className={styles.discoverySection}>
-          {totalSchools && <p className={styles.discoveryCount}><strong>{totalSchools.toLocaleString()}+</strong> primary schools across England</p>}
+          {totalSchools && <p className={styles.discoveryCount}><strong>{totalSchools.toLocaleString()}+</strong> primary and secondary schools across England</p>}
           <p className={styles.discoveryHints}>Try searching for a school name, or enter a postcode to find schools near you.</p>
           <div className={styles.quickSearches}>
             <span className={styles.quickSearchLabel}>Quick searches:</span>
@@ -258,7 +258,14 @@ function CompactSchoolItem({ school, onAddToCompare, isInCompare }: CompactSchoo
         </div>
         <div className={styles.compactItemStats}>
           <span className={styles.compactStat}>
-            <strong>{school.rwm_expected_pct !== null ? `${school.rwm_expected_pct}%` : '-'}</strong> RWM
+            <strong>
+              {school.attainment_8_score != null
+                ? school.attainment_8_score.toFixed(1)
+                : school.rwm_expected_pct !== null
+                  ? `${school.rwm_expected_pct}%`
+                  : '-'}
+            </strong>{' '}
+            {school.attainment_8_score != null ? 'Att 8' : 'RWM'}
           </span>
           <span className={styles.compactStat}>
             <strong>{school.total_pupils || '-'}</strong> pupils
diff --git a/nextjs-app/components/MetricTooltip.module.css b/nextjs-app/components/MetricTooltip.module.css
new file mode 100644
index 0000000..a11b84f
--- /dev/null
+++ b/nextjs-app/components/MetricTooltip.module.css
@@ -0,0 +1,83 @@
+.wrapper {
+  position: relative;
+  display: inline-flex;
+  align-items: center;
+  margin-left: 0.3em;
+}
+
+.icon {
+  font-size: 0.85em;
+  color: var(--text-muted, #8a7a72);
+  cursor: help;
+  line-height: 1;
+  user-select: none;
+  transition: color 0.15s ease;
+}
+
+.wrapper:hover .icon {
+  color: var(--accent-coral, #e07256);
+}
+
+.tooltip {
+  visibility: hidden;
+  opacity: 0;
+  position: absolute;
+  bottom: calc(100% + 6px);
+  left: 50%;
+  transform: translateX(-50%);
+  z-index: 9999;
+  width: 220px;
+  background: var(--bg-primary, #faf7f2);
+  border: 1px solid var(--border-color, #e8ddd4);
+  border-radius: 10px;
+  box-shadow: 0 4px 16px rgba(44, 36, 32, 0.15);
+  padding: 0.6rem 0.75rem;
+  display: flex;
+  flex-direction: column;
+  gap: 0.3rem;
+  pointer-events: none;
+  transition: opacity 0.15s ease, visibility 0.15s ease;
+}
+
+/* Keep tooltip visible when hovering over it */
+.wrapper:hover .tooltip {
+  visibility: visible;
+  opacity: 1;
+}
+
+/* Small arrow pointing down */
+.tooltip::after {
+  content: '';
+  position: absolute;
+  top: 100%;
+  left: 50%;
+  transform: translateX(-50%);
+  border: 5px solid transparent;
+  border-top-color: var(--border-color, #e8ddd4);
+}
+
+.tooltipLabel {
+  font-weight: 600;
+  font-size: 0.75rem;
+  color: var(--text-primary, #2c2420);
+}
+
+.tooltipPlain {
+  font-size: 0.75rem;
+  color: var(--text-secondary, #5a4a44);
+  line-height: 1.4;
+}
+
+.tooltipDetail {
+  font-size: 0.7rem;
+  color: var(--text-muted, #8a7a72);
+  line-height: 1.4;
+  margin-top: 0.1rem;
+}
+
+/* Flip tooltip below when near top of screen */
+@media (max-width: 480px) {
+  .tooltip {
+    width: 180px;
+  }
+}
diff --git a/nextjs-app/components/MetricTooltip.tsx b/nextjs-app/components/MetricTooltip.tsx
new file mode 100644
index 0000000..8021926
--- /dev/null
+++ b/nextjs-app/components/MetricTooltip.tsx
@@ -0,0 +1,31 @@
+'use client';
+
+import { METRIC_EXPLANATIONS } from '@/lib/metrics';
+import styles from './MetricTooltip.module.css';
+
+interface MetricTooltipProps {
+  metricKey?: string;
+  label?: string;
+  plain?: string;
+  detail?: string;
+}
+
+export function MetricTooltip({ metricKey, label, plain, detail }: MetricTooltipProps) {
+  const explanation = metricKey ? METRIC_EXPLANATIONS[metricKey] : undefined;
+  const tooltipLabel = label ?? explanation?.label;
+  const tooltipPlain = plain ?? explanation?.plain;
+  const tooltipDetail = detail ?? explanation?.detail;
+
+  if (!tooltipPlain) return null;
+
+  return (
+    <span className={styles.wrapper}>
+      <span className={styles.icon} aria-label={tooltipLabel ?? 'More information'} role="img">ⓘ</span>
+      <span className={styles.tooltip} role="tooltip">
+        {tooltipLabel && <span className={styles.tooltipLabel}>{tooltipLabel}</span>}
+        <span className={styles.tooltipPlain}>{tooltipPlain}</span>
+        {tooltipDetail && <span className={styles.tooltipDetail}>{tooltipDetail}</span>}
+      </span>
+    </span>
+  );
+}
diff --git a/nextjs-app/components/PerformanceChart.tsx b/nextjs-app/components/PerformanceChart.tsx
index e377fde..79a2f7a 100644
--- a/nextjs-app/components/PerformanceChart.tsx
+++ b/nextjs-app/components/PerformanceChart.tsx
@@ -34,24 +34,50 @@ ChartJS.register(
 interface PerformanceChartProps {
   data: SchoolResult[];
   schoolName: string;
+  isSecondary?: boolean;
 }
 
-export function PerformanceChart({ data, schoolName }: PerformanceChartProps) {
+export function PerformanceChart({ data, schoolName, isSecondary = false }: PerformanceChartProps) {
   // Sort data by year
   const sortedData = [...data].sort((a, b) => a.year - b.year);
   const years = sortedData.map(d => d.year.toString());
 
-  // Prepare datasets
-  const datasets = [
+  // Prepare datasets — phase-aware
+  const datasets = isSecondary ? [
     {
-      label: 'RWM Expected %',
+      label: 'Attainment 8',
+      data: sortedData.map(d => d.attainment_8_score),
+      borderColor: 'rgb(59, 130, 246)',
+      backgroundColor: 'rgba(59, 130, 246, 0.1)',
+      tension: 0.3,
+      yAxisID: 'y',
+    },
+    {
+      label: 'English & Maths Grade 4+',
+      data: sortedData.map(d => d.english_maths_standard_pass_pct),
+      borderColor: 'rgb(16, 185, 129)',
+      backgroundColor: 'rgba(16, 185, 129, 0.1)',
+      tension: 0.3,
+      yAxisID: 'y',
+    },
+    {
+      label: 'Progress 8',
+      data: sortedData.map(d => d.progress_8_score),
+      borderColor: 'rgb(245, 158, 11)',
+      backgroundColor: 'rgba(245, 158, 11, 0.1)',
+      tension: 0.3,
+      yAxisID: 'y1',
+    },
+  ] : [
+    {
+      label: 'Reading, Writing & Maths Expected %',
       data: sortedData.map(d => d.rwm_expected_pct),
       borderColor: 'rgb(59, 130, 246)',
       backgroundColor: 'rgba(59, 130, 246, 0.1)',
       tension: 0.3,
     },
     {
-      label: 'RWM Higher %',
+      label: 'Reading, Writing & Maths Higher %',
       data: sortedData.map(d => d.rwm_high_pct),
       borderColor: 'rgb(16, 185, 129)',
       backgroundColor: 'rgba(16, 185, 129, 0.1)',
@@ -153,14 +179,14 @@ export function PerformanceChart({ data, schoolName }: PerformanceChartProps) {
         position: 'left' as const,
         title: {
           display: true,
-          text: 'Percentage (%)',
+          text: isSecondary ? 'Score / Percentage (%)' : 'Percentage (%)',
           font: {
             size: 12,
             weight: 'bold',
           },
         },
         min: 0,
-        max: 100,
+        max: isSecondary ? undefined : 100,
         grid: {
           color: 'rgba(0, 0, 0, 0.05)',
         },
@@ -171,7 +197,7 @@ export function PerformanceChart({ data, schoolName }: PerformanceChartProps) {
         position: 'right' as const,
         title: {
           display: true,
-          text: 'Progress Score',
+          text: isSecondary ? 'Progress 8 Score' : 'Progress Score',
           font: {
             size: 12,
             weight: 'bold',
diff --git a/nextjs-app/components/SchoolCard.tsx b/nextjs-app/components/SchoolCard.tsx
index 8658466..f99addc 100644
--- a/nextjs-app/components/SchoolCard.tsx
+++ b/nextjs-app/components/SchoolCard.tsx
@@ -48,12 +48,35 @@ export function SchoolCard({ school, onAddToCompare, onRemoveFromCompare, showDi
         )}
       </div>
 
-      {(school.rwm_expected_pct !== null || school.reading_progress !== null) && (
+      {(school.rwm_expected_pct != null || school.attainment_8_score != null || school.reading_progress !== null) && (
         <div className={styles.metrics}>
+          {/* KS4 card metrics for secondary schools */}
+          {school.attainment_8_score != null && (
+            <div className={styles.metric}>
+              <span className={styles.metricLabel}>
+                Attainment 8
+                <span className={styles.metricHint}>avg grade across best 8 GCSEs</span>
+              </span>
+              <div className={styles.metricValue}>
+                <strong>{school.attainment_8_score.toFixed(1)}</strong>
+              </div>
+            </div>
+          )}
+          {school.english_maths_standard_pass_pct != null && (
+            <div className={styles.metric}>
+              <span className={styles.metricLabel}>
+                English &amp; Maths Grade 4+
+                <span className={styles.metricHint}>% standard pass in both</span>
+              </span>
+              <div className={styles.metricValue}>
+                <strong>{formatPercentage(school.english_maths_standard_pass_pct)}</strong>
+              </div>
+            </div>
+          )}
           {school.rwm_expected_pct !== null && (
             <div className={styles.metric}>
               <span className={styles.metricLabel}>
-                RWM Expected
+                Reading, Writing &amp; Maths
                 <span className={styles.metricHint}>% meeting expected standard</span>
               </span>
               <div className={styles.metricValue}>
diff --git a/nextjs-app/components/SchoolDetailView.tsx b/nextjs-app/components/SchoolDetailView.tsx
index 23ea2ac..0794dc6 100644
--- a/nextjs-app/components/SchoolDetailView.tsx
+++ b/nextjs-app/components/SchoolDetailView.tsx
@@ -5,15 +5,17 @@
 
 'use client';
 
+import { useEffect, useState } from 'react';
 import { useRouter } from 'next/navigation';
 import { useComparison } from '@/hooks/useComparison';
 import { PerformanceChart } from './PerformanceChart';
 import { SchoolMap } from './SchoolMap';
+import { MetricTooltip } from './MetricTooltip';
 import type {
   School, SchoolResult, AbsenceData,
   OfstedInspection, OfstedParentView, SchoolCensus,
   SchoolAdmissions, SenDetail, Phonics,
-  SchoolDeprivation, SchoolFinance,
+  SchoolDeprivation, SchoolFinance, NationalAverages,
 } from '@/lib/types';
 import { formatPercentage, formatProgress, formatAcademicYear } from '@/lib/utils';
 import styles from './SchoolDetailView.module.css';
@@ -37,19 +39,6 @@ const RC_CATEGORIES = [
   { key: 'rc_sixth_form' as const,            label: 'Sixth Form' },
 ];
 
-// 2023 national averages for context
-const NATIONAL_AVG = {
-  rwm_expected: 60,
-  rwm_high: 8,
-  reading_expected: 73,
-  writing_expected: 71,
-  maths_expected: 73,
-  phonics_yr1: 79,
-  overall_absence: 6.7,
-  persistent_absence: 22,
-  class_size: 27,
-  per_pupil_spend: 6000,
-};
 
 function progressClass(val: number | null | undefined): string {
   if (val == null) return '';
@@ -82,6 +71,23 @@ export function SchoolDetailView({
 
   const latestResults = yearlyData.length > 0 ? yearlyData[yearlyData.length - 1] : null;
 
+  // Phase detection
+  const phase = schoolInfo.phase ?? '';
+  const isSecondary = phase.toLowerCase().includes('secondary') || phase.toLowerCase() === 'all-through';
+  const isPrimary = !isSecondary;
+
+  // National averages (fetched dynamically so they stay current)
+  const [nationalAvg, setNationalAvg] = useState<NationalAverages | null>(null);
+  useEffect(() => {
+    fetch('/api/national-averages')
+      .then(r => r.ok ? r.json() : null)
+      .then(data => { if (data) setNationalAvg(data); })
+      .catch(() => {});
+  }, []);
+
+  const primaryAvg = nationalAvg?.primary ?? {};
+  const secondaryAvg = nationalAvg?.secondary ?? {};
+
   const handleComparisonToggle = () => {
     if (isInComparison) {
       removeSchool(schoolInfo.urn);
@@ -108,13 +114,18 @@ export function SchoolDetailView({
   const hasFinance = finance != null && finance.per_pupil_spend != null;
   const hasLocation = schoolInfo.latitude != null && schoolInfo.longitude != null;
 
+  // Determine whether this school has KS2 or KS4 results to show
+  const hasKS2Results = latestResults != null && latestResults.rwm_expected_pct != null;
+  const hasKS4Results = latestResults != null && latestResults.attainment_8_score != null;
+  const hasAnyResults = hasKS2Results || hasKS4Results;
+
   // Build section nav items dynamically — only sections with data
   const navItems: { id: string; label: string }[] = [];
   if (ofsted) navItems.push({ id: 'ofsted', label: 'Ofsted' });
   if (parentView && parentView.total_responses != null && parentView.total_responses > 0)
     navItems.push({ id: 'parents', label: 'Parents' });
-  if (latestResults) navItems.push({ id: 'sats', label: 'SATs' });
-  if (hasPhonics) navItems.push({ id: 'phonics', label: 'Phonics' });
+  if (hasAnyResults) navItems.push({ id: 'results', label: isSecondary ? 'GCSEs' : 'SATs' });
+  if (hasPhonics && isPrimary) navItems.push({ id: 'phonics', label: 'Phonics' });
   if (hasSchoolLife) navItems.push({ id: 'school-life', label: 'School Life' });
   if (admissions) navItems.push({ id: 'admissions', label: 'Admissions' });
   if (hasInclusionData) navItems.push({ id: 'inclusion', label: 'Pupils' });
@@ -328,135 +339,259 @@ export function SchoolDetailView({
         </section>
       )}
 
-      {/* SATs Results (merged with Subject Breakdown) */}
-      {latestResults && (
-        <section id="sats" className={styles.card}>
-          <h2 className={styles.sectionTitle}>SATs Results ({formatAcademicYear(latestResults.year)})</h2>
+      {/* Results Section (SATs for primary, GCSEs for secondary) */}
+      {hasAnyResults && latestResults && (
+        <section id="results" className={styles.card}>
+          <h2 className={styles.sectionTitle}>
+            {isSecondary ? 'GCSE Results' : 'SATs Results'} ({formatAcademicYear(latestResults.year)})
+          </h2>
           <p className={styles.sectionSubtitle}>
-            End-of-primary-school tests taken by Year 6 pupils. National averages shown for comparison.
+            {isSecondary
+              ? 'GCSE results for Year 11 pupils. National averages shown for comparison.'
+              : 'End-of-primary-school tests taken by Year 6 pupils. National averages shown for comparison.'}
           </p>
 
-          {/* Headline numbers: RWM combined */}
-          <div className={styles.metricsGrid}>
-            {latestResults.rwm_expected_pct !== null && (
-              <div className={styles.metricCard}>
-                <div className={styles.metricLabel}>Reading, Writing & Maths combined</div>
-                <div className={styles.metricValue}>{formatPercentage(latestResults.rwm_expected_pct)}</div>
-                <div className={styles.metricHint}>National avg: {NATIONAL_AVG.rwm_expected}%</div>
+          {/* ── Primary / KS2 content ── */}
+          {hasKS2Results && (
+            <>
+              <div className={styles.metricsGrid}>
+                {latestResults.rwm_expected_pct !== null && (
+                  <div className={styles.metricCard}>
+                    <div className={styles.metricLabel}>
+                      Reading, Writing &amp; Maths combined
+                      <MetricTooltip metricKey="rwm_expected_pct" />
+                    </div>
+                    <div className={styles.metricValue}>{formatPercentage(latestResults.rwm_expected_pct)}</div>
+                    {primaryAvg.rwm_expected_pct != null && (
+                      <div className={styles.metricHint}>National avg: {primaryAvg.rwm_expected_pct.toFixed(0)}%</div>
+                    )}
+                  </div>
+                )}
+                {latestResults.rwm_high_pct !== null && (
+                  <div className={styles.metricCard}>
+                    <div className={styles.metricLabel}>
+                      Exceeding expected level (Reading, Writing &amp; Maths)
+                      <MetricTooltip metricKey="rwm_high_pct" />
+                    </div>
+                    <div className={styles.metricValue}>{formatPercentage(latestResults.rwm_high_pct)}</div>
+                    {primaryAvg.rwm_high_pct != null && (
+                      <div className={styles.metricHint}>National avg: {primaryAvg.rwm_high_pct.toFixed(0)}%</div>
+                    )}
+                  </div>
+                )}
               </div>
-            )}
-            {latestResults.rwm_high_pct !== null && (
-              <div className={styles.metricCard}>
-                <div className={styles.metricLabel}>Exceeding expected level (RWM)</div>
-                <div className={styles.metricValue}>{formatPercentage(latestResults.rwm_high_pct)}</div>
-                <div className={styles.metricHint}>National avg: {NATIONAL_AVG.rwm_high}%</div>
-              </div>
-            )}
-          </div>
 
-          {/* Per-subject detail table */}
-          <div className={styles.metricGroupsGrid} style={{ marginTop: '1rem' }}>
-            <div className={styles.metricGroup}>
-              <h3 className={styles.metricGroupTitle}>Reading</h3>
-              <div className={styles.metricTable}>
-                {latestResults.reading_expected_pct !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Expected level</span>
-                    <span className={styles.metricValue}>{formatPercentage(latestResults.reading_expected_pct)}</span>
+              <div className={styles.metricGroupsGrid} style={{ marginTop: '1rem' }}>
+                <div className={styles.metricGroup}>
+                  <h3 className={styles.metricGroupTitle}>Reading</h3>
+                  <div className={styles.metricTable}>
+                    {latestResults.reading_expected_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>Expected level</span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.reading_expected_pct)}</span>
+                      </div>
+                    )}
+                    {latestResults.reading_high_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>Exceeding</span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.reading_high_pct)}</span>
+                      </div>
+                    )}
+                    {latestResults.reading_progress !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>
+                          Progress score
+                          <MetricTooltip metricKey="reading_progress" />
+                        </span>
+                        <span className={`${styles.metricValue} ${progressClass(latestResults.reading_progress)}`}>
+                          {formatProgress(latestResults.reading_progress)}
+                        </span>
+                      </div>
+                    )}
+                    {latestResults.reading_avg_score !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>
+                          Average score
+                          <MetricTooltip metricKey="reading_avg_score" />
+                        </span>
+                        <span className={styles.metricValue}>{latestResults.reading_avg_score.toFixed(1)}</span>
+                      </div>
+                    )}
+                  </div>
+                </div>
+
+                <div className={styles.metricGroup}>
+                  <h3 className={styles.metricGroupTitle}>Writing</h3>
+                  <div className={styles.metricTable}>
+                    {latestResults.writing_expected_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>Expected level</span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.writing_expected_pct)}</span>
+                      </div>
+                    )}
+                    {latestResults.writing_high_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>Exceeding</span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.writing_high_pct)}</span>
+                      </div>
+                    )}
+                    {latestResults.writing_progress !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>
+                          Progress score
+                          <MetricTooltip metricKey="writing_progress" />
+                        </span>
+                        <span className={`${styles.metricValue} ${progressClass(latestResults.writing_progress)}`}>
+                          {formatProgress(latestResults.writing_progress)}
+                        </span>
+                      </div>
+                    )}
+                  </div>
+                </div>
+
+                <div className={styles.metricGroup}>
+                  <h3 className={styles.metricGroupTitle}>Maths</h3>
+                  <div className={styles.metricTable}>
+                    {latestResults.maths_expected_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>Expected level</span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.maths_expected_pct)}</span>
+                      </div>
+                    )}
+                    {latestResults.maths_high_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>Exceeding</span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.maths_high_pct)}</span>
+                      </div>
+                    )}
+                    {latestResults.maths_progress !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>
+                          Progress score
+                          <MetricTooltip metricKey="maths_progress" />
+                        </span>
+                        <span className={`${styles.metricValue} ${progressClass(latestResults.maths_progress)}`}>
+                          {formatProgress(latestResults.maths_progress)}
+                        </span>
+                      </div>
+                    )}
+                    {latestResults.maths_avg_score !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>
+                          Average score
+                          <MetricTooltip metricKey="maths_avg_score" />
+                        </span>
+                        <span className={styles.metricValue}>{latestResults.maths_avg_score.toFixed(1)}</span>
+                      </div>
+                    )}
+                  </div>
+                </div>
+              </div>
+
+              {(latestResults.reading_progress !== null || latestResults.writing_progress !== null || latestResults.maths_progress !== null) && (
+                <p className={styles.progressNote}>
+                  Progress scores measure how much pupils improved compared to similar schools nationally. Above 0 = better than average, below 0 = below average.
+                </p>
+              )}
+            </>
+          )}
+
+          {/* ── Secondary / KS4 content ── */}
+          {hasKS4Results && (
+            <>
+              <div className={styles.metricsGrid}>
+                {latestResults.attainment_8_score !== null && (
+                  <div className={styles.metricCard}>
+                    <div className={styles.metricLabel}>
+                      Attainment 8
+                      <MetricTooltip metricKey="attainment_8_score" />
+                    </div>
+                    <div className={styles.metricValue}>{latestResults.attainment_8_score.toFixed(1)}</div>
+                    {secondaryAvg.attainment_8_score != null && (
+                      <div className={styles.metricHint}>National avg: {secondaryAvg.attainment_8_score.toFixed(1)}</div>
+                    )}
                   </div>
                 )}
-                {latestResults.reading_high_pct !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Exceeding</span>
-                    <span className={styles.metricValue}>{formatPercentage(latestResults.reading_high_pct)}</span>
+                {latestResults.progress_8_score !== null && (
+                  <div className={styles.metricCard}>
+                    <div className={styles.metricLabel}>
+                      Progress 8
+                      <MetricTooltip metricKey="progress_8_score" />
+                    </div>
+                    <div className={`${styles.metricValue} ${progressClass(latestResults.progress_8_score)}`}>
+                      {formatProgress(latestResults.progress_8_score)}
+                    </div>
+                    <div className={styles.metricHint}>0 = national average</div>
                   </div>
                 )}
-                {latestResults.reading_progress !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Progress score</span>
-                    <span className={`${styles.metricValue} ${progressClass(latestResults.reading_progress)}`}>
-                      {formatProgress(latestResults.reading_progress)}
-                    </span>
+                {latestResults.english_maths_standard_pass_pct !== null && (
+                  <div className={styles.metricCard}>
+                    <div className={styles.metricLabel}>
+                      English &amp; Maths Grade 4+
+                      <MetricTooltip metricKey="english_maths_standard_pass_pct" />
+                    </div>
+                    <div className={styles.metricValue}>{formatPercentage(latestResults.english_maths_standard_pass_pct)}</div>
+                    {secondaryAvg.english_maths_standard_pass_pct != null && (
+                      <div className={styles.metricHint}>National avg: {secondaryAvg.english_maths_standard_pass_pct.toFixed(0)}%</div>
+                    )}
                   </div>
                 )}
-                {latestResults.reading_avg_score !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Average score</span>
-                    <span className={styles.metricValue}>{latestResults.reading_avg_score.toFixed(1)}</span>
+                {latestResults.english_maths_strong_pass_pct !== null && (
+                  <div className={styles.metricCard}>
+                    <div className={styles.metricLabel}>
+                      English &amp; Maths Grade 5+
+                      <MetricTooltip metricKey="english_maths_strong_pass_pct" />
+                    </div>
+                    <div className={styles.metricValue}>{formatPercentage(latestResults.english_maths_strong_pass_pct)}</div>
+                    {secondaryAvg.english_maths_strong_pass_pct != null && (
+                      <div className={styles.metricHint}>National avg: {secondaryAvg.english_maths_strong_pass_pct.toFixed(0)}%</div>
+                    )}
                   </div>
                 )}
               </div>
-            </div>
 
-            <div className={styles.metricGroup}>
-              <h3 className={styles.metricGroupTitle}>Writing</h3>
-              <div className={styles.metricTable}>
-                {latestResults.writing_expected_pct !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Expected level</span>
-                    <span className={styles.metricValue}>{formatPercentage(latestResults.writing_expected_pct)}</span>
+              {/* EBacc */}
+              {(latestResults.ebacc_entry_pct !== null || latestResults.ebacc_standard_pass_pct !== null) && (
+                <>
+                  <h3 className={styles.subSectionTitle} style={{ marginTop: '1rem' }}>
+                    English Baccalaureate (EBacc)
+                    <MetricTooltip metricKey="ebacc_entry_pct" />
+                  </h3>
+                  <div className={styles.metricTable}>
+                    {latestResults.ebacc_entry_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>Pupils entered for EBacc</span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.ebacc_entry_pct)}</span>
+                      </div>
+                    )}
+                    {latestResults.ebacc_standard_pass_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>
+                          EBacc Grade 4+
+                          <MetricTooltip metricKey="ebacc_standard_pass_pct" />
+                        </span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.ebacc_standard_pass_pct)}</span>
+                      </div>
+                    )}
+                    {latestResults.ebacc_strong_pass_pct !== null && (
+                      <div className={styles.metricRow}>
+                        <span className={styles.metricName}>
+                          EBacc Grade 5+
+                          <MetricTooltip metricKey="ebacc_strong_pass_pct" />
+                        </span>
+                        <span className={styles.metricValue}>{formatPercentage(latestResults.ebacc_strong_pass_pct)}</span>
+                      </div>
+                    )}
                   </div>
-                )}
-                {latestResults.writing_high_pct !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Exceeding</span>
-                    <span className={styles.metricValue}>{formatPercentage(latestResults.writing_high_pct)}</span>
-                  </div>
-                )}
-                {latestResults.writing_progress !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Progress score</span>
-                    <span className={`${styles.metricValue} ${progressClass(latestResults.writing_progress)}`}>
-                      {formatProgress(latestResults.writing_progress)}
-                    </span>
-                  </div>
-                )}
-              </div>
-            </div>
-
-            <div className={styles.metricGroup}>
-              <h3 className={styles.metricGroupTitle}>Maths</h3>
-              <div className={styles.metricTable}>
-                {latestResults.maths_expected_pct !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Expected level</span>
-                    <span className={styles.metricValue}>{formatPercentage(latestResults.maths_expected_pct)}</span>
-                  </div>
-                )}
-                {latestResults.maths_high_pct !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Exceeding</span>
-                    <span className={styles.metricValue}>{formatPercentage(latestResults.maths_high_pct)}</span>
-                  </div>
-                )}
-                {latestResults.maths_progress !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Progress score</span>
-                    <span className={`${styles.metricValue} ${progressClass(latestResults.maths_progress)}`}>
-                      {formatProgress(latestResults.maths_progress)}
-                    </span>
-                  </div>
-                )}
-                {latestResults.maths_avg_score !== null && (
-                  <div className={styles.metricRow}>
-                    <span className={styles.metricName}>Average score</span>
-                    <span className={styles.metricValue}>{latestResults.maths_avg_score.toFixed(1)}</span>
-                  </div>
-                )}
-              </div>
-            </div>
-          </div>
-
-          {(latestResults.reading_progress !== null || latestResults.writing_progress !== null || latestResults.maths_progress !== null) && (
-            <p className={styles.progressNote}>
-              Progress scores measure how much pupils improved compared to similar schools nationally. Above 0 = better than average, below 0 = below average.
-            </p>
+                </>
+              )}
+            </>
           )}
         </section>
       )}
 
-      {/* Year 1 Phonics */}
-      {hasPhonics && phonics && (
+      {/* Year 1 Phonics — primary only */}
+      {hasPhonics && isPrimary && phonics && (
         <section id="phonics" className={styles.card}>
           <h2 className={styles.sectionTitle}>Year 1 Phonics ({formatAcademicYear(phonics.year)})</h2>
           <p className={styles.sectionSubtitle}>
@@ -466,7 +601,7 @@ export function SchoolDetailView({
             <div className={styles.metricCard}>
               <div className={styles.metricLabel}>Passed the phonics check</div>
               <div className={styles.metricValue}>{formatPercentage(phonics.year1_phonics_pct)}</div>
-              <div className={styles.metricHint}>National avg: ~{NATIONAL_AVG.phonics_yr1}%</div>
+              <div className={styles.metricHint}>Phonics is a key early reading skill tested at end of Year 1</div>
             </div>
             {phonics.year2_phonics_pct != null && (
               <div className={styles.metricCard}>
@@ -487,21 +622,31 @@ export function SchoolDetailView({
               <div className={styles.metricCard}>
                 <div className={styles.metricLabel}>Average class size</div>
                 <div className={styles.metricValue}>{census.class_size_avg.toFixed(1)}</div>
-                <div className={styles.metricHint}>National avg: ~{NATIONAL_AVG.class_size} pupils</div>
+                <div className={styles.metricHint}>Average number of pupils per class</div>
               </div>
             )}
             {absenceData?.overall_absence_rate != null && (
               <div className={styles.metricCard}>
-                <div className={styles.metricLabel}>Days missed (overall absence)</div>
+                <div className={styles.metricLabel}>
+                  Days missed (overall absence)
+                  <MetricTooltip metricKey="overall_absence_pct" />
+                </div>
                 <div className={styles.metricValue}>{formatPercentage(absenceData.overall_absence_rate)}</div>
-                <div className={styles.metricHint}>National avg: ~{NATIONAL_AVG.overall_absence}%</div>
+                {primaryAvg.overall_absence_pct != null && (
+                  <div className={styles.metricHint}>National avg: ~{primaryAvg.overall_absence_pct.toFixed(1)}%</div>
+                )}
               </div>
             )}
             {absenceData?.persistent_absence_rate != null && (
               <div className={styles.metricCard}>
-                <div className={styles.metricLabel}>Regularly missing school</div>
+                <div className={styles.metricLabel}>
+                  Regularly missing school
+                  <MetricTooltip metricKey="persistent_absence_pct" />
+                </div>
                 <div className={styles.metricValue}>{formatPercentage(absenceData.persistent_absence_rate)}</div>
-                <div className={styles.metricHint}>National avg: ~{NATIONAL_AVG.persistent_absence}%. Missing 10%+ of sessions.</div>
+                {primaryAvg.persistent_absence_pct != null && (
+                  <div className={styles.metricHint}>National avg: ~{primaryAvg.persistent_absence_pct.toFixed(0)}%</div>
+                )}
               </div>
             )}
           </div>
@@ -515,7 +660,7 @@ export function SchoolDetailView({
           <div className={styles.metricsGrid}>
             {admissions.published_admission_number != null && (
               <div className={styles.metricCard}>
-                <div className={styles.metricLabel}>Year 3 places per year</div>
+                <div className={styles.metricLabel}>{isSecondary ? 'Year 7' : 'Year 3'} places per year</div>
                 <div className={styles.metricValue}>{admissions.published_admission_number}</div>
               </div>
             )}
@@ -556,13 +701,19 @@ export function SchoolDetailView({
             )}
             {latestResults?.eal_pct != null && (
               <div className={styles.metricCard}>
-                <div className={styles.metricLabel}>English as an additional language</div>
+                <div className={styles.metricLabel}>
+                  English as an additional language
+                  <MetricTooltip metricKey="eal_pct" />
+                </div>
                 <div className={styles.metricValue}>{formatPercentage(latestResults.eal_pct)}</div>
               </div>
             )}
             {latestResults?.sen_support_pct != null && (
               <div className={styles.metricCard}>
-                <div className={styles.metricLabel}>Pupils with additional needs (SEN support)</div>
+                <div className={styles.metricLabel}>
+                  Pupils receiving SEN support
+                  <MetricTooltip metricKey="sen_support_pct" />
+                </div>
                 <div className={styles.metricValue}>{formatPercentage(latestResults.sen_support_pct)}</div>
               </div>
             )}
@@ -610,7 +761,10 @@ export function SchoolDetailView({
       {/* Local Area Context */}
       {hasDeprivation && deprivation && (
         <section id="local-area" className={styles.card}>
-          <h2 className={styles.sectionTitle}>Local Area Context</h2>
+          <h2 className={styles.sectionTitle}>
+          Local Area Context
+          <MetricTooltip metricKey="idaci_decile" />
+        </h2>
           <div className={styles.deprivationDots}>
             {Array.from({ length: 10 }, (_, i) => (
               <div
@@ -639,7 +793,7 @@ export function SchoolDetailView({
             <div className={styles.metricCard}>
               <div className={styles.metricLabel}>Total spend per pupil per year</div>
               <div className={styles.metricValue}>£{Math.round(finance.per_pupil_spend!).toLocaleString()}</div>
-              <div className={styles.metricHint}>National avg: ~£{NATIONAL_AVG.per_pupil_spend.toLocaleString()}</div>
+              <div className={styles.metricHint}>How much the school has to spend on each pupil annually</div>
             </div>
             {finance.teacher_cost_pct != null && (
               <div className={styles.metricCard}>
@@ -665,6 +819,7 @@ export function SchoolDetailView({
             <PerformanceChart
               data={yearlyData}
               schoolName={schoolInfo.school_name}
+              isSecondary={isSecondary}
             />
           </div>
           {yearlyData.length > 1 && (
@@ -675,22 +830,44 @@ export function SchoolDetailView({
                   <thead>
                     <tr>
                       <th>Year</th>
-                      <th>Reading, Writing & Maths (expected %)</th>
-                      <th>Exceeding expected (%)</th>
-                      <th>Reading Progress</th>
-                      <th>Writing Progress</th>
-                      <th>Maths Progress</th>
+                      {isSecondary ? (
+                        <>
+                          <th>Attainment 8</th>
+                          <th>Progress 8</th>
+                          <th>English &amp; Maths Grade 4+</th>
+                          <th>English &amp; Maths Grade 5+</th>
+                        </>
+                      ) : (
+                        <>
+                          <th>Reading, Writing &amp; Maths (expected %)</th>
+                          <th>Exceeding expected (%)</th>
+                          <th>Reading Progress</th>
+                          <th>Writing Progress</th>
+                          <th>Maths Progress</th>
+                        </>
+                      )}
                     </tr>
                   </thead>
                   <tbody>
                     {yearlyData.map((result) => (
                       <tr key={result.year}>
                         <td className={styles.yearCell}>{formatAcademicYear(result.year)}</td>
-                        <td>{result.rwm_expected_pct !== null ? formatPercentage(result.rwm_expected_pct) : '-'}</td>
-                        <td>{result.rwm_high_pct !== null ? formatPercentage(result.rwm_high_pct) : '-'}</td>
-                        <td>{result.reading_progress !== null ? formatProgress(result.reading_progress) : '-'}</td>
-                        <td>{result.writing_progress !== null ? formatProgress(result.writing_progress) : '-'}</td>
-                        <td>{result.maths_progress !== null ? formatProgress(result.maths_progress) : '-'}</td>
+                        {isSecondary ? (
+                          <>
+                            <td>{result.attainment_8_score !== null ? result.attainment_8_score.toFixed(1) : '-'}</td>
+                            <td>{result.progress_8_score !== null ? formatProgress(result.progress_8_score) : '-'}</td>
+                            <td>{result.english_maths_standard_pass_pct !== null ? formatPercentage(result.english_maths_standard_pass_pct) : '-'}</td>
+                            <td>{result.english_maths_strong_pass_pct !== null ? formatPercentage(result.english_maths_strong_pass_pct) : '-'}</td>
+                          </>
+                        ) : (
+                          <>
+                            <td>{result.rwm_expected_pct !== null ? formatPercentage(result.rwm_expected_pct) : '-'}</td>
+                            <td>{result.rwm_high_pct !== null ? formatPercentage(result.rwm_high_pct) : '-'}</td>
+                            <td>{result.reading_progress !== null ? formatProgress(result.reading_progress) : '-'}</td>
+                            <td>{result.writing_progress !== null ? formatProgress(result.writing_progress) : '-'}</td>
+                            <td>{result.maths_progress !== null ? formatProgress(result.maths_progress) : '-'}</td>
+                          </>
+                        )}
                       </tr>
                     ))}
                   </tbody>
diff --git a/nextjs-app/lib/metrics.ts b/nextjs-app/lib/metrics.ts
index e679a45..56effec 100644
--- a/nextjs-app/lib/metrics.ts
+++ b/nextjs-app/lib/metrics.ts
@@ -98,6 +98,66 @@ export const METRIC_EXPLANATIONS: Record<string, MetricExplanation> = {
     plain: 'Difference in attainment between disadvantaged pupils and their peers',
     detail: 'A smaller gap means the school is doing more to support disadvantaged pupils.',
   },
+  sen_support_pct: {
+    label: 'SEN Support',
+    plain: '% of pupils receiving SEN (Special Educational Needs) support without a formal plan',
+    detail: 'These pupils need extra help but do not yet have an Education, Health and Care Plan (EHCP).',
+  },
+  sen_ehcp_pct: {
+    label: 'Education, Health and Care Plan (EHCP)',
+    plain: '% of pupils with a formal EHCP — a legal plan for pupils with significant additional needs',
+  },
+  eal_pct: {
+    label: 'English as an Additional Language',
+    plain: '% of pupils whose first language is not English',
+  },
+  idaci_decile: {
+    label: 'Deprivation (IDACI)',
+    plain: 'How deprived the area around the school is. Decile 1 = most deprived 10% of areas in England.',
+    detail: 'IDACI stands for Income Deprivation Affecting Children Index. It measures the proportion of children living in low-income households in an area.',
+  },
+  // ── KS4 / GCSE metrics ────────────────────────────────────────────────
+  attainment_8_score: {
+    label: 'Attainment 8',
+    plain: 'Average grade across a pupil\'s best 8 GCSEs, including English and Maths',
+    detail: 'Each GCSE grade is converted to a points score (grade 9 = 9 points, grade 1 = 1 point). The national average is around 46.',
+  },
+  progress_8_score: {
+    label: 'Progress 8',
+    plain: 'How much pupils improved from their primary school results to GCSE, compared to similar pupils nationally',
+    detail: '0 = national average. Positive means better-than-expected progress; negative means lower-than-expected. A score above +0.5 is considered well above average.',
+  },
+  english_maths_standard_pass_pct: {
+    label: 'English & Maths — Grade 4+ (Standard Pass)',
+    plain: '% of pupils achieving at least a grade 4 in both English and Maths',
+    detail: 'Grade 4 is the minimum "standard pass". Employers and colleges often require grade 4 in English and Maths.',
+  },
+  english_maths_strong_pass_pct: {
+    label: 'English & Maths — Grade 5+ (Strong Pass)',
+    plain: '% of pupils achieving at least a grade 5 in both English and Maths',
+    detail: 'Grade 5 is a "strong pass". Many sixth forms and universities expect grade 5 in English and Maths.',
+  },
+  ebacc_entry_pct: {
+    label: 'EBacc Entry',
+    plain: '% of pupils who entered the English Baccalaureate — a set of GCSE subjects covering English, Maths, Sciences, a Language, and Humanities',
+    detail: 'EBacc entry keeps academic options open post-16. It is not a separate qualification.',
+  },
+  ebacc_standard_pass_pct: {
+    label: 'EBacc — Grade 4+ (Standard Pass)',
+    plain: '% of pupils achieving grade 4 or above across all EBacc subjects',
+  },
+  ebacc_strong_pass_pct: {
+    label: 'EBacc — Grade 5+ (Strong Pass)',
+    plain: '% of pupils achieving grade 5 or above across all EBacc subjects',
+  },
+  ebacc_avg_score: {
+    label: 'EBacc Average Score',
+    plain: 'Average points score across all EBacc subject entries',
+  },
+  gcse_grade_91_pct: {
+    label: 'GCSE Grade 9–1 %',
+    plain: '% of GCSE entries where a pupil achieved a grade between 9 (highest) and 1',
+  },
 };
 
 /**
diff --git a/nextjs-app/lib/types.ts b/nextjs-app/lib/types.ts
index ba9ecb7..7dbe5c7 100644
--- a/nextjs-app/lib/types.ts
+++ b/nextjs-app/lib/types.ts
@@ -48,6 +48,13 @@ export interface School {
   // Location search fields
   distance?: number | null;
 
+  // Phase (Primary, Secondary, All-through, etc.)
+  phase?: string | null;
+
+  // KS4 card metrics
+  attainment_8_score?: number | null;
+  english_maths_standard_pass_pct?: number | null;
+
   // GIAS enrichment fields
   website?: string | null;
   headteacher_name?: string | null;
@@ -225,6 +232,24 @@ export interface SchoolResult {
   rwm_expected_3yr_pct: number | null;
   reading_avg_3yr: number | null;
   maths_avg_3yr: number | null;
+
+  // KS4 / GCSE metrics
+  attainment_8_score: number | null;
+  progress_8_score: number | null;
+  progress_8_lower_ci: number | null;
+  progress_8_upper_ci: number | null;
+  progress_8_english: number | null;
+  progress_8_maths: number | null;
+  progress_8_ebacc: number | null;
+  progress_8_open: number | null;
+  english_maths_strong_pass_pct: number | null;
+  english_maths_standard_pass_pct: number | null;
+  ebacc_entry_pct: number | null;
+  ebacc_strong_pass_pct: number | null;
+  ebacc_standard_pass_pct: number | null;
+  ebacc_avg_score: number | null;
+  gcse_grade_91_pct: number | null;
+  prior_attainment_avg: number | null;
 }
 
 // ============================================================================
@@ -304,6 +329,13 @@ export interface Filters {
   local_authorities: string[];
   school_types: string[];
   years: number[];
+  phases: string[];
+}
+
+export interface NationalAverages {
+  year: number;
+  primary: Record<string, number>;
+  secondary: Record<string, number>;
 }
 
 // Backend returns filters directly, not wrapped
@@ -338,6 +370,7 @@ export interface SchoolSearchParams {
   search?: string;
   local_authority?: string;
   school_type?: string;
+  phase?: string;
   postcode?: string;
   radius?: number;
   page?: number;