diff --git a/backend/app.py b/backend/app.py
index a054a6b..15bf139 100644
--- a/backend/app.py
+++ b/backend/app.py
@@ -621,6 +621,19 @@ def verify_admin_api_key(x_api_key: str = Header(None)) -> bool:
     return True
 
 
+def _with_whole_school_pupils(rows: pd.DataFrame, source: pd.DataFrame) -> pd.DataFrame:
+    """Set total_pupils to the size of the school.
+
+    fact_performance's total_pupils is the cohort a year's results were
+    measured on. For a secondary that is the GCSE year group alone (Burntwood:
+    245 against 1,462 on roll). Cards, map popups and place rows label it
+    "pupils", so they take the register's whole-school count instead, and
+    nothing when the register has none.
+    """
+    whole = source["gias_total_pupils"] if "gias_total_pupils" in source.columns else None
+    return rows.assign(total_pupils=whole)
+
+
 # Input validation helpers
 def _names_in_group(names: pd.Series, in_group) -> set:
     """The distinct names in a column that a group predicate accepts.
@@ -859,7 +872,7 @@ async def get_schools(
         if c in df_latest.columns
     ]
     # fact_performance guarantees one row per (urn, year); df_latest has one row per urn.
-    schools_df = df_latest[available_cols]
+    schools_df = _with_whole_school_pupils(df_latest[available_cols], df_latest)
 
     # Location-based search (uses pre-geocoded data from database)
     search_coords = None
@@ -1545,7 +1558,7 @@ async def get_place(request: Request, kind: str, slug: str,
                   # variants that exist rather than 404s.
                   "phases": [ph for ph in ("primary", "secondary")
                              if place.publishes_phase(ph)]},
-        "schools": clean_for_json(rows[cols]),
+        "schools": clean_for_json(_with_whole_school_pupils(rows[cols], rows)),
         "averages": averages,
     }
 
diff --git a/backend/tests/test_whole_school_pupils.py b/backend/tests/test_whole_school_pupils.py
new file mode 100644
index 0000000..8e9e8a7
--- /dev/null
+++ b/backend/tests/test_whole_school_pupils.py
@@ -0,0 +1,67 @@
+"""Cards, map popups and place rows label total_pupils "pupils".
+
+fact_performance's total_pupils is the cohort a year's results were measured
+on. For a secondary that is the GCSE year group alone: Burntwood showed 245 in
+search against 1,462 on roll. The list and place payloads therefore carry the
+register's whole-school count, and nothing when the register has none.
+"""
+
+import numpy as np
+import pandas as pd
+import pytest
+from fastapi.testclient import TestClient
+
+
+def _schools_df() -> pd.DataFrame:
+    base = {
+        "local_authority": "Essex", "school_type": "Academy converter",
+        "year": 202425, "ofsted_grade": 2.0, "ofsted_date": None,
+        "town": "Brentwood", "postcode": "CM13 1AA", "status": "Open",
+        "address": "1 Test Street", "latitude": 51.6, "longitude": 0.3,
+        "gender": "Mixed", "rwm_expected_pct": np.nan, "attainment_8_score": 50.0,
+    }
+    rows = [
+        # Secondary: results cohort 245, register 1,462.
+        {**base, "urn": 100001, "school_name": "Alpha High", "phase": "Secondary",
+         "total_pupils": 245, "gias_total_pupils": 1462},
+        # Register count missing: no count, never the cohort.
+        {**base, "urn": 100002, "school_name": "Beta High", "phase": "Secondary",
+         "total_pupils": 180, "gias_total_pupils": np.nan},
+    ]
+    # Enough schools in one town for it to have a place page.
+    rows += [
+        {**base, "urn": 100010 + i, "school_name": f"Gamma High {i}", "phase": "Secondary",
+         "total_pupils": 200, "gias_total_pupils": 1000 + i}
+        for i in range(5)
+    ]
+    return pd.DataFrame(rows)
+
+
+@pytest.fixture()
+def client(monkeypatch):
+    from backend import app as app_module
+
+    monkeypatch.setattr(app_module, "load_latest_school_data", _schools_df)
+    monkeypatch.setattr(app_module, "load_school_data", _schools_df)
+    monkeypatch.setattr(app_module, "_place_registry", None)
+    return TestClient(app_module.app, raise_server_exceptions=False)
+
+
+def _pupils(schools: list[dict]) -> dict[int, object]:
+    return {s["urn"]: s.get("total_pupils") for s in schools}
+
+
+def test_the_list_carries_the_whole_school_count(client):
+    resp = client.get("/api/schools?page_size=50")
+    assert resp.status_code == 200, resp.text
+    pupils = _pupils(resp.json()["schools"])
+    assert pupils[100001] == 1462
+    assert pupils[100002] is None
+
+
+def test_a_place_page_carries_the_whole_school_count(client):
+    resp = client.get("/api/places/town/brentwood")
+    assert resp.status_code == 200, resp.text
+    pupils = _pupils(resp.json()["schools"])
+    assert pupils[100001] == 1462
+    assert pupils[100002] is None
diff --git a/nextjs-app/__tests__/components/schoolPupilCount.test.tsx b/nextjs-app/__tests__/components/schoolPupilCount.test.tsx
new file mode 100644
index 0000000..d5d792f
--- /dev/null
+++ b/nextjs-app/__tests__/components/schoolPupilCount.test.tsx
@@ -0,0 +1,56 @@
+/**
+ * "Pupils" on a school page is the size of the school.
+ *
+ * A year's results row carries the cohort its figures were measured on. For a
+ * secondary that is the GCSE year group alone (Burntwood: 245, against 1,462
+ * on roll), so it must never stand in for the whole-school count.
+ */
+
+import { screen } from '@testing-library/react';
+import { secondaryFixture } from '../support/schoolFixtures';
+import { renderSecondarySchoolDetail } from '../support/renderSchoolDetail';
+
+jest.mock('@/lib/analytics', () => ({
+  track: jest.fn(),
+  getNavigationSource: () => 'direct',
+}));
+jest.mock('@/components/PerformanceChart', () => ({
+  PerformanceChart: () => <div data-testid="performance-chart" />,
+}));
+jest.mock('@/components/SatsChart', () => ({
+  __esModule: true,
+  default: () => <div data-testid="sats-chart" />,
+}));
+jest.mock('@/components/AdmissionsTrendChart', () => ({
+  __esModule: true,
+  default: () => <div data-testid="admissions-trend-chart" />,
+}));
+jest.mock('@/components/SchoolHeroMap', () => ({
+  SchoolHeroMap: () => <div data-testid="hero-map" />,
+  __esModule: true,
+}));
+
+function withoutCensus(schoolTotal: number | null) {
+  const yearlyData = secondaryFixture.yearlyData.map((r) => ({ ...r, total_pupils: 245 }));
+  return {
+    ...secondaryFixture,
+    census: null,
+    yearlyData,
+    schoolInfo: { ...secondaryFixture.schoolInfo, total_pupils: schoolTotal },
+  };
+}
+
+describe('pupil count without a census record', () => {
+  it('uses the register count in the header, not the results cohort', () => {
+    renderSecondarySchoolDetail(withoutCensus(1462));
+    const pupils = screen.getByText('Pupils:').parentElement!;
+    expect(pupils).toHaveTextContent('1,462');
+    expect(pupils).not.toHaveTextContent('245');
+  });
+
+  it('shows no count rather than the results cohort when the register has none', () => {
+    renderSecondarySchoolDetail(withoutCensus(null));
+    expect(screen.queryByText('Pupils:')).not.toBeInTheDocument();
+    expect(screen.queryByText('Total pupils')).not.toBeInTheDocument();
+  });
+});
diff --git a/nextjs-app/__tests__/support/renderSchoolDetail.tsx b/nextjs-app/__tests__/support/renderSchoolDetail.tsx
index acc657d..5ab2b60 100644
--- a/nextjs-app/__tests__/support/renderSchoolDetail.tsx
+++ b/nextjs-app/__tests__/support/renderSchoolDetail.tsx
@@ -39,7 +39,6 @@ export function renderSchoolDetail(fixture: any) {
     withProviders(
       <SchoolDetailShell
         schoolInfo={fixture.schoolInfo}
-        yearlyData={fixture.yearlyData}
         census={fixture.census}
         navItems={navItems}
       >
@@ -67,7 +66,6 @@ export function renderSecondarySchoolDetail(fixture: any) {
     withProviders(
       <SchoolDetailShell
         schoolInfo={fixture.schoolInfo}
-        yearlyData={fixture.yearlyData}
         census={fixture.census}
         navItems={navItems}
       >
diff --git a/nextjs-app/app/(frontend)/school/[slug]/page.tsx b/nextjs-app/app/(frontend)/school/[slug]/page.tsx
index 838ab67..a083de4 100644
--- a/nextjs-app/app/(frontend)/school/[slug]/page.tsx
+++ b/nextjs-app/app/(frontend)/school/[slug]/page.tsx
@@ -249,7 +249,6 @@ export default async function SchoolPage({ params }: SchoolPageProps) {
       {isSecondary ? (
         <SchoolDetailShell
           schoolInfo={school_info}
-          yearlyData={yearly_data}
           census={census ?? null}
           navItems={secondaryNavItems}
         >
@@ -273,7 +272,6 @@ export default async function SchoolPage({ params }: SchoolPageProps) {
       ) : (
         <SchoolDetailShell
           schoolInfo={school_info}
-          yearlyData={yearly_data}
           census={census ?? null}
           navItems={primaryNavItems}
         >
diff --git a/nextjs-app/components/school/SchoolDetailShell.tsx b/nextjs-app/components/school/SchoolDetailShell.tsx
index ff031ca..2e0bd88 100644
--- a/nextjs-app/components/school/SchoolDetailShell.tsx
+++ b/nextjs-app/components/school/SchoolDetailShell.tsx
@@ -34,8 +34,6 @@ import styles from './SchoolDetailShell.module.css';
  */
 export interface SchoolDetailShellProps {
   schoolInfo: School;
-  /** Only for the header's pupil-count fallback. */
-  yearlyData: SchoolResult[];
   census: SchoolCensus | null;
   /** Section list for the sticky nav, computed on the server. */
   navItems: NavItem[];
@@ -44,7 +42,7 @@ export interface SchoolDetailShellProps {
 }
 
 export function SchoolDetailShell({
-  schoolInfo, yearlyData, census, navItems, children,
+  schoolInfo, census, navItems, children,
 }: SchoolDetailShellProps) {
   const router = useRouter();
   const { addSchool, removeSchool, isSelected } = useComparison();
@@ -126,7 +124,6 @@ export function SchoolDetailShell({
   // once on the server (lib/schoolSections) and consumed by the section
   // composers; recomputing them here would duplicate that work for values
   // this component never renders.
-  const latestResults = yearlyData.length > 0 ? yearlyData[yearlyData.length - 1] : null;
   const phase = schoolInfo.phase ?? '';
   const isAllThrough = phase.toLowerCase() === 'all-through';
   const hasLocation = schoolInfo.latitude != null && schoolInfo.longitude != null;
@@ -283,7 +280,9 @@ export function SchoolDetailShell({
                 </span>
               )}
               {(() => {
-                const total = census?.total_pupils ?? latestResults?.total_pupils ?? null;
+                // Never latestResults.total_pupils: that is the results
+                // cohort, which for a secondary is the GCSE year group alone.
+                const total = census?.total_pupils ?? schoolInfo.total_pupils ?? null;
                 if (total == null) return null;
                 return (
                   <span className={styles.headerDetail}>
diff --git a/nextjs-app/components/school/WellbeingSection.tsx b/nextjs-app/components/school/WellbeingSection.tsx
index 93fef14..7a1e035 100644
--- a/nextjs-app/components/school/WellbeingSection.tsx
+++ b/nextjs-app/components/school/WellbeingSection.tsx
@@ -54,7 +54,8 @@ export function WellbeingSection({
               </div>
             )}
             {(() => {
-              const total = census?.total_pupils ?? schoolInfo.total_pupils ?? latestResults?.total_pupils ?? null;
+              // Not latestResults.total_pupils: that is the GCSE year group.
+              const total = census?.total_pupils ?? schoolInfo.total_pupils ?? null;
               if (total == null) return null;
               const female = census?.female_pupils ?? null;
               const male = census?.male_pupils ?? null;