fix(detail): compare each SATs bar to its own national benchmark

The KS2 SATs chart drew a single national-average line spanning the
full height of each subject's chart area, positioned at the national
*expected* value. But the area stacks two bars — Expected and Exceeding
— and the higher-standard/greater-depth national is a very different,
much lower figure (e.g. reading higher standard ~29% vs expected ~75%).
So the line crossed the Exceeding bar at the wrong place, making every
school's exceeding result look far below national when it wasn't.

The per-subject higher-standard nationals were already computed in the
fact_ks2_national_averages mart; they just weren't serialized. Fix:

- backend: add reading_high_pct, writing_gd_pct (writing = greater
  depth) and maths_high_pct to the national-averages payload.
- SchoolDetailView: pass a nationalExceedingPct per subject, mapping
  writing to the greater-depth figure.
- SatsChart: replace the single full-height line with a national marker
  on each bar's own track (coral tick + "nat X%" in the bar header), so
  Expected and Exceeding each sit against the correct benchmark.

KS2 only; the secondary Attainment 8 chart already uses one line for
one measure and is untouched.

Verified: tsc --noEmit, next build, and backend pytest (national
averages marts, incl. a new test guarding the per-subject nationals).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

backend/app.py

@@ -807,6 +807,10 @@ async def get_la_averages(request: Request):
 _KS2_NATIONAL_METRICS = [
     "rwm_expected_pct", "rwm_high_pct",
     "reading_expected_pct", "writing_expected_pct", "maths_expected_pct",
+    # Per-subject higher-standard nationals: reading/maths reach the "higher
+    # standard" in the tests; writing is teacher-assessed at "greater depth"
+    # (writing_gd_pct). Needed so each SATs bar compares to its own benchmark.
+    "reading_high_pct", "writing_gd_pct", "maths_high_pct",
     "gps_expected_pct", "gps_high_pct", "science_expected_pct",
     "reading_avg_score", "maths_avg_score", "gps_avg_score",
     "reading_progress", "writing_progress", "maths_progress",

backend/tests/test_national_averages_marts.py

@@ -25,6 +25,11 @@ class _Ks2Row:
     year = LATEST
     rwm_expected_pct = 62.1
     gps_expected_pct = 72.0
+    # Per-subject higher-standard nationals — reading/maths reach the higher
+    # standard, writing is teacher-assessed at greater depth (writing_gd_pct).
+    reading_high_pct = 29.0
+    writing_gd_pct = 13.0
+    maths_high_pct = 24.0
 
 
 class _Ks4Row:
@@ -84,6 +89,16 @@ def test_ks4_averages_come_from_the_mart_not_the_dataframe(payload):
     assert body["by_year"][-1]["secondary"]["progress_8_score"] == -0.02
 
 
+def test_per_subject_higher_standard_nationals_are_surfaced(payload):
+    # The SATs chart compares each bar to its own benchmark, so the per-subject
+    # higher-standard / greater-depth nationals must reach the payload — not
+    # only the combined rwm_high_pct.
+    body = payload(_StubSession)
+    assert body["primary"]["reading_high_pct"] == 29.0
+    assert body["primary"]["writing_gd_pct"] == 13.0
+    assert body["primary"]["maths_high_pct"] == 24.0
+
+
 def test_ks4_secondary_empty_when_mart_missing(payload):
     # No computed stand-in: the UI labels national figures as official DfE
     # data, so an empty mart must yield an empty secondary series.

nextjs-app/components/SatsChart.module.css

@@ -44,30 +44,46 @@
   background: var(--bg-secondary, #f3ede4);
 }
 
-/* ── National average marker ── */
-.natLine {
+/* ── Per-bar national average marker ──
+   Each bar compares against its own benchmark (expected vs higher standard /
+   greater depth), so the marker sits on the individual bar's track rather than
+   as one line spanning both bars. */
+.natTick {
   position: absolute;
-  top: 0;
-  height: calc(100% - 20px);
-  width: 1.5px;
-  background: rgba(224, 114, 86, 0.35); /* --accent-coral at 35% */
-  z-index: 2;
+  top: -3px;
+  bottom: -3px;
+  width: 2px;
+  transform: translateX(-50%);
+  background: var(--accent-coral, #e07256);
+  border-radius: 2px;
+  z-index: 4;
   pointer-events: none;
 }
 
-.natPill {
+.natTick::before {
+  content: '';
   position: absolute;
-  top: -10px;
+  top: -3px;
+  left: 50%;
   transform: translateX(-50%);
+  width: 5px;
+  height: 5px;
+  border-radius: 50%;
   background: var(--accent-coral, #e07256);
-  color: #fff;
+}
+
+.barHeaderRight {
+  display: flex;
+  align-items: baseline;
+  gap: 0.4rem;
+}
+
+.natLabel {
   font-size: 0.55rem;
   font-weight: 700;
-  padding: 0.1rem 0.35rem;
-  border-radius: 4px;
-  white-space: nowrap;
-  z-index: 3;
-  letter-spacing: 0.02em;
+  color: var(--accent-coral-dark, #b04a2e);
+  text-transform: uppercase;
+  letter-spacing: 0.03em;
 }
 
 /* ── Bar rows ── */

nextjs-app/components/SatsChart.tsx

@@ -8,6 +8,9 @@ interface SubjectData {
   expectedPct: number | null;
   exceedingPct: number | null;
   nationalExpectedPct: number | null;
+  /** National higher-standard / greater-depth benchmark for the exceeding
+   * bar — a different figure from the expected national. */
+  nationalExceedingPct: number | null;
 }
 
 interface SatsChartProps {
@@ -17,11 +20,45 @@ interface SatsChartProps {
 const RULER_TICKS = [0, 25, 50, 75, 100];
 const GRIDLINE_POSITIONS = [25, 50, 75];
 
+/** One results bar with a national marker positioned on its own track, so the
+ * expected and exceeding bars each compare against their own benchmark. */
+function BarRow({
+  label,
+  value,
+  national,
+  barRef,
+  barClass,
+}: {
+  label: string;
+  value: number;
+  national: number | null;
+  barRef: React.RefObject<HTMLDivElement | null>;
+  barClass: string;
+}) {
+  return (
+    <div className={styles.barRow}>
+      <div className={styles.barHeader}>
+        <span className={styles.barLabelSuffix}>{label}</span>
+        <span className={styles.barHeaderRight}>
+          {national != null && <span className={styles.natLabel}>nat {national.toFixed(0)}%</span>}
+          <span className={styles.barLabel}>{value.toFixed(0)}%</span>
+        </span>
+      </div>
+      <div className={styles.barTrack}>
+        <div ref={barRef} className={`${styles.bar} ${barClass}`} data-width={value} />
+        {national != null && (
+          <div className={styles.natTick} style={{ left: `${national}%` }} aria-hidden="true" />
+        )}
+      </div>
+    </div>
+  );
+}
+
 function SubjectColumn({ subject }: { subject: SubjectData }) {
   const expectedRef = useRef<HTMLDivElement>(null);
   const exceedingRef = useRef<HTMLDivElement>(null);
 
-  const { name, expectedPct, exceedingPct, nationalExpectedPct } = subject;
+  const { name, expectedPct, exceedingPct, nationalExpectedPct, nationalExceedingPct } = subject;
 
   // Animate bars on mount
   useEffect(() => {
@@ -51,44 +88,25 @@ function SubjectColumn({ subject }: { subject: SubjectData }) {
           ))}
         </div>
 
-        {/* National average marker */}
-        {nationalExpectedPct != null && (
-          <div className={styles.natLine} style={{ left: `${nationalExpectedPct}%` }}>
-            <div className={styles.natPill}>{nationalExpectedPct.toFixed(0)}%</div>
-          </div>
-        )}
-
-        {/* Bars */}
+        {/* Bars — each carries its own national marker */}
         <div className={styles.barGroup}>
           {expectedPct != null && (
-            <div className={styles.barRow}>
-              <div className={styles.barHeader}>
-                <span className={styles.barLabelSuffix}>Expected</span>
-                <span className={styles.barLabel}>{expectedPct.toFixed(0)}%</span>
-              </div>
-              <div className={styles.barTrack}>
-                <div
-                  ref={expectedRef}
-                  className={`${styles.bar} ${styles.barExpected}`}
-                  data-width={expectedPct}
-                />
-              </div>
-            </div>
+            <BarRow
+              label="Expected"
+              value={expectedPct}
+              national={nationalExpectedPct}
+              barRef={expectedRef}
+              barClass={styles.barExpected}
+            />
           )}
           {exceedingPct != null && (
-            <div className={styles.barRow}>
-              <div className={styles.barHeader}>
-                <span className={styles.barLabelSuffix}>Exceeding</span>
-                <span className={styles.barLabel}>{exceedingPct.toFixed(0)}%</span>
-              </div>
-              <div className={styles.barTrack}>
-                <div
-                  ref={exceedingRef}
-                  className={`${styles.bar} ${styles.barExceeding}`}
-                  data-width={exceedingPct}
-                />
-              </div>
-            </div>
+            <BarRow
+              label="Exceeding"
+              value={exceedingPct}
+              national={nationalExceedingPct}
+              barRef={exceedingRef}
+              barClass={styles.barExceeding}
+            />
           )}
         </div>
 
@@ -135,7 +153,7 @@ export default function SatsChart({ subjects }: SatsChartProps) {
           Exceeding / high score
         </div>
         <div className={styles.legendItem}>
-          <div className={styles.legendSwatch} style={{ background: 'var(--accent-coral, #e07256)', borderRadius: '50%' }} />
+          <div className={styles.legendSwatch} style={{ background: 'var(--accent-coral, #e07256)', width: '3px', height: '12px', borderRadius: '2px' }} />
           National average
         </div>
       </div>

nextjs-app/components/SchoolDetailView.tsx

@@ -752,18 +752,22 @@ export function SchoolDetailView({
                       expectedPct: latestResults.reading_expected_pct,
                       exceedingPct: latestResults.reading_high_pct,
                       nationalExpectedPct: suppressKs2Comparison ? null : primaryAvg.reading_expected_pct,
+                      nationalExceedingPct: suppressKs2Comparison ? null : primaryAvg.reading_high_pct,
                     },
                     {
                       name: 'Writing',
                       expectedPct: latestResults.writing_expected_pct,
                       exceedingPct: latestResults.writing_high_pct,
                       nationalExpectedPct: suppressKs2Comparison ? null : primaryAvg.writing_expected_pct,
+                      // Writing's higher level is teacher-assessed "greater depth".
+                      nationalExceedingPct: suppressKs2Comparison ? null : primaryAvg.writing_gd_pct,
                     },
                     {
                       name: 'Maths',
                       expectedPct: latestResults.maths_expected_pct,
                       exceedingPct: latestResults.maths_high_pct,
                       nationalExpectedPct: suppressKs2Comparison ? null : primaryAvg.maths_expected_pct,
+                      nationalExceedingPct: suppressKs2Comparison ? null : primaryAvg.maths_high_pct,
                     },
                   ]}
                 />