refactor(detail): extract derived flags and nav items to lib

Pure data-shape logic moves out of the client components so page.tsx can
compute the section list on the server without importing them.

The secondary page is not a variant of the primary one -- different section
ids (gcse, wellbeing), different flags, and History gated on more than one
year rather than at least one -- so it gets its own computeSecondaryFlags and
buildSecondaryNavItems rather than bending a shared function.

Adds 16 unit tests covering the all-through and special-school branches,
previously reachable only through a full component render.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

nextjs-app/__tests__/lib/schoolSections.test.ts

@@ -0,0 +1,144 @@
+import {
+  computeSchoolFlags, buildNavItems,
+  computeSecondaryFlags, buildSecondaryNavItems,
+} from '@/lib/schoolSections';
+import {
+  primaryFixture, secondaryFixture, allThroughFixture, specialFixture,
+} from '../support/schoolFixtures';
+
+describe('computeSchoolFlags', () => {
+  it('treats an all-through school as both primary-capable and secondary', () => {
+    const f = computeSchoolFlags(allThroughFixture);
+    expect(f.isAllThrough).toBe(true);
+    expect(f.isSecondary).toBe(true);
+    expect(f.hasKS2Results).toBe(true);
+    expect(f.hasKS4Results).toBe(true);
+  });
+
+  it('classifies an ordinary primary', () => {
+    const f = computeSchoolFlags(primaryFixture);
+    expect(f.isPrimary).toBe(true);
+    expect(f.isSecondary).toBe(false);
+    expect(f.hasKS2Results).toBe(true);
+    expect(f.hasKS4Results).toBe(false);
+  });
+
+  it('classifies an ordinary secondary', () => {
+    const f = computeSchoolFlags(secondaryFixture);
+    expect(f.isSecondary).toBe(true);
+    expect(f.isAllThrough).toBe(false);
+    expect(f.hasKS4Results).toBe(true);
+  });
+
+  it('suppresses the KS2 comparison for a special school', () => {
+    const f = computeSchoolFlags(specialFixture);
+    expect(f.isSpecial).toBe(true);
+    expect(f.suppressKs2Comparison).toBe(true);
+    expect(f.suppressKs4Comparison).toBe(true);
+  });
+
+  it('treats an all-zero KS2 row as a placeholder', () => {
+    const f = computeSchoolFlags(specialFixture);
+    expect(f.ks2Placeholder).toBe(true);
+  });
+
+  it('does not suppress comparison for an ordinary primary', () => {
+    const f = computeSchoolFlags(primaryFixture);
+    expect(f.isSpecial).toBe(false);
+    expect(f.suppressKs2Comparison).toBe(false);
+  });
+
+  it('detects a gender split only when census counts are present', () => {
+    expect(computeSchoolFlags(primaryFixture).hasGenderSplit).toBe(true);
+    expect(
+      computeSchoolFlags({ ...primaryFixture, census: null }).hasGenderSplit,
+    ).toBe(false);
+  });
+});
+
+describe('buildNavItems', () => {
+  it('omits sections with no data', () => {
+    const flags = computeSchoolFlags(specialFixture);
+    const ids = buildNavItems(flags, {
+      ofsted: null, admissions: null, yearlyDataLength: 1,
+    }).map((n) => n.id);
+
+    expect(ids).not.toContain('ofsted');
+    expect(ids).not.toContain('admissions');
+    expect(ids).toContain('history');
+  });
+
+  it('labels the results section by phase', () => {
+    const label = (fixture: any) => {
+      const flags = computeSchoolFlags(fixture);
+      return buildNavItems(flags, {
+        ofsted: fixture.ofsted,
+        admissions: fixture.admissions,
+        yearlyDataLength: fixture.yearlyData.length,
+      }).find((n) => n.id === 'results')?.label;
+    };
+
+    expect(label(primaryFixture)).toBe('SATs');
+    expect(label(secondaryFixture)).toBe('GCSEs');
+    expect(label(allThroughFixture)).toBe('Results');
+  });
+
+  it('keeps the engagement-led ordering', () => {
+    const flags = computeSchoolFlags(primaryFixture);
+    const ids = buildNavItems(flags, {
+      ofsted: primaryFixture.ofsted,
+      admissions: primaryFixture.admissions,
+      yearlyDataLength: primaryFixture.yearlyData.length,
+    }).map((n) => n.id);
+
+    expect(ids).toEqual([
+      'ofsted', 'results', 'admissions', 'inclusion',
+      'history', 'school-life', 'local-area', 'finances',
+    ]);
+  });
+});
+
+describe('computeSecondaryFlags', () => {
+  it('reads results and sixth form from the secondary fixture', () => {
+    const f = computeSecondaryFlags(secondaryFixture);
+    expect(f.hasResults).toBe(true);
+    expect(f.hasSixthForm).toBe(false);
+    expect(f.hasWellbeing).toBe(true);
+  });
+
+  it('reports sixth form when GIAS flags it', () => {
+    expect(computeSecondaryFlags(allThroughFixture).hasSixthForm).toBe(true);
+  });
+
+  it('suppresses the comparison for a special school', () => {
+    const f = computeSecondaryFlags(specialFixture);
+    expect(f.isSpecial).toBe(true);
+    expect(f.suppressComparison).toBe(true);
+  });
+
+  it('does not flag Progress 8 as suspended for pre-2024/25 cohorts', () => {
+    expect(computeSecondaryFlags(secondaryFixture).p8Suspended).toBe(false);
+  });
+});
+
+describe('buildSecondaryNavItems', () => {
+  it('uses the secondary section ids', () => {
+    const flags = computeSecondaryFlags(secondaryFixture);
+    const ids = buildSecondaryNavItems(flags, {
+      ofsted: secondaryFixture.ofsted,
+      admissions: secondaryFixture.admissions,
+      yearlyDataLength: secondaryFixture.yearlyData.length,
+    }).map((n) => n.id);
+
+    expect(ids).toEqual(['ofsted', 'gcse', 'admissions', 'history', 'wellbeing', 'finances']);
+  });
+
+  it('gates History on more than one year, unlike the primary page', () => {
+    const flags = computeSecondaryFlags(secondaryFixture);
+    const ids = buildSecondaryNavItems(flags, {
+      ofsted: null, admissions: null, yearlyDataLength: 1,
+    }).map((n) => n.id);
+
+    expect(ids).not.toContain('history');
+  });
+});

nextjs-app/components/SchoolDetailView.tsx

@@ -18,8 +18,9 @@ import type {
   SchoolDeprivation, SchoolFinance, NationalAverages,
 } from '@/lib/types';
 import {
-  formatPercentage, formatProgress, formatAcademicYear, formatAgeRange, isProposedToClose, ofstedLegacyAreas, isSpecialSchool,
+  formatPercentage, formatProgress, formatAcademicYear, formatAgeRange, isProposedToClose, ofstedLegacyAreas,
 } from '@/lib/utils';
+import { computeSchoolFlags, buildNavItems } from '@/lib/schoolSections';
 import { DeltaChip } from './DeltaChip';
 import { SpecialSchoolNote } from './SpecialSchoolNote';
 import { summariseAdmissions } from '@/lib/compareLogic';
@@ -162,16 +163,18 @@ export function SchoolDetailView({
     return () => window.removeEventListener('keydown', onKey);
   }, [sectionsOpen]);
 
-  const latestResults = yearlyData.length > 0 ? yearlyData[yearlyData.length - 1] : null;
-
-  // Phase detection. All-through schools cover BOTH key stages, so they are
-  // neither "pure primary" nor "pure secondary": isSecondary stays true (they
-  // have KS4 data) but isAllThrough gates the primary-only content (KS2 SATs,
-  // KS2 trend) back on and switches phase-specific copy to an all-ages framing.
+  // Derived data-shape logic lives in lib/schoolSections so the server route
+  // can compute the section list without importing this client component.
+  const flags = computeSchoolFlags({
+    schoolInfo, yearlyData, absenceData, census, deprivation, finance,
+  });
+  const {
+    latestResults, isAllThrough, isSecondary, isPrimary,
+    hasGenderSplit, hasInclusionData, hasSchoolLife, hasDeprivation,
+    hasFinance, hasLocation, hasKS2Results, hasKS4Results, hasAnyResults,
+    isSpecial, ks2Placeholder, suppressKs2Comparison, suppressKs4Comparison,
+  } = flags;
   const phase = schoolInfo.phase ?? '';
-  const isAllThrough = phase.toLowerCase() === 'all-through';
-  const isSecondary = phase.toLowerCase().includes('secondary') || isAllThrough;
-  const isPrimary = !isSecondary;
 
   const primaryAvg = nationalAvg?.primary ?? {};
   const secondaryAvg = nationalAvg?.secondary ?? {};
@@ -203,63 +206,9 @@ export function SchoolDetailView({
     return `This school is in one of England's less deprived areas (decile ${decile}/10).`;
   };
 
-  // Gender split availability (only meaningful for Mixed schools with census data)
-  const isMixedSchool = schoolInfo.gender === 'Mixed' || schoolInfo.gender == null;
-  const hasGenderSplit = isMixedSchool
-    && census?.female_pupils != null
-    && census?.male_pupils != null
-    && (census.female_pupils + census.male_pupils) > 0;
-
-  // Guard for Pupils & Inclusion — only show if at least one metric is available
-  const hasInclusionData = (latestResults?.disadvantaged_pct != null)
-    || (latestResults?.eal_pct != null)
-    || (latestResults?.sen_support_pct != null)
-    || hasGenderSplit;
-
-  const hasSchoolLife = absenceData != null;
-  const hasDeprivation = deprivation != null && deprivation.idaci_decile != null;
-  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;
-
-  // Special schools / PRUs / AP: their pupils sit the same tests but very few
-  // reach the mainstream "expected standard", so a 0% headline and an England
-  // comparison portray them as failing against a benchmark that doesn't fit.
-  const isSpecial = isSpecialSchool(schoolInfo);
-  // Belt-and-braces for KS2: a whole-row zero attainment (every subject 0 — a
-  // special/suppressed signature) is a placeholder, not a real result. This
-  // needs ALL of RWM + reading + writing + maths to be 0, so a genuine 0%
-  // combined (some pupils met individual subjects but not all three) stays
-  // comparable. Attainment 8 is a single 0–80 score with no subject breakdown
-  // to form such a signature, so KS4 keys off establishment type only — a
-  // genuine (if extreme) 0.0 still shows its real figure and comparison.
-  const ks2Placeholder = latestResults != null
-    && latestResults.rwm_expected_pct === 0
-    && (latestResults.reading_expected_pct ?? 0) === 0
-    && (latestResults.writing_expected_pct ?? 0) === 0
-    && (latestResults.maths_expected_pct ?? 0) === 0;
-  // Whether to drop the England-average deltas / national markers / "below"
-  // framing on the attainment measures.
-  const suppressKs2Comparison = isSpecial || ks2Placeholder;
-  const suppressKs4Comparison = isSpecial;
-
-  // Build section nav items dynamically — only sections with data.
-  // Order is engagement-led (from section_nav_used analytics): the most-sought
-  // sections — results, admissions, inclusion, history — sit near the top,
-  // after the recognised Ofsted badge; low-demand context sections stay last.
-  const navItems: { id: string; label: string }[] = [];
-  if (ofsted) navItems.push({ id: 'ofsted', label: 'Ofsted' });
-  if (hasAnyResults) navItems.push({ id: 'results', label: isAllThrough ? 'Results' : isSecondary ? 'GCSEs' : 'SATs' });
-  if (admissions) navItems.push({ id: 'admissions', label: 'Admissions' });
-  if (hasInclusionData) navItems.push({ id: 'inclusion', label: 'Pupils' });
-  if (yearlyData.length > 0) navItems.push({ id: 'history', label: 'History' });
-  if (hasSchoolLife) navItems.push({ id: 'school-life', label: 'School Life' });
-  if (hasDeprivation) navItems.push({ id: 'local-area', label: 'Local Area' });
-  if (hasFinance) navItems.push({ id: 'finances', label: 'Finances' });
+  const navItems = buildNavItems(flags, {
+    ofsted, admissions, yearlyDataLength: yearlyData.length,
+  });
 
   // Track active section as user scrolls
   useEffect(() => {

nextjs-app/components/SecondarySchoolDetailView.tsx

@@ -23,7 +23,8 @@ import type {
   SchoolAdmissions,
   SchoolDeprivation, SchoolFinance, NationalAverages,
 } from '@/lib/types';
-import { formatPercentage, formatProgress, formatAcademicYear, formatAgeRange, isProposedToClose, ofstedLegacyAreas, isSpecialSchool } from '@/lib/utils';
+import { formatPercentage, formatProgress, formatAcademicYear, formatAgeRange, isProposedToClose, ofstedLegacyAreas } from '@/lib/utils';
+import { computeSecondaryFlags, buildSecondaryNavItems } from '@/lib/schoolSections';
 import { DeltaChip } from './DeltaChip';
 import { SpecialSchoolNote } from './SpecialSchoolNote';
 import { track, getNavigationSource } from '@/lib/analytics';
@@ -90,29 +91,16 @@ export function SecondarySchoolDetailView({
   // Header details collapse behind a "Show all details" link on mobile/tablet.
   const [detailsOpen, setDetailsOpen] = useState(false);
 
-  const latestResults = yearlyData.length > 0 ? yearlyData[yearlyData.length - 1] : null;
+  // Derived data-shape logic lives in lib/schoolSections so the server route
+  // can compute the section list without importing this client component.
+  const flags = computeSecondaryFlags({ schoolInfo, yearlyData, deprivation, finance });
+  const {
+    latestResults, hasSixthForm, hasFinance, hasDeprivation, hasLocation,
+    hasWellbeing, hasResults, p8Suspended, isSpecial, suppressComparison,
+  } = flags;
 
   const secondaryAvg = nationalAvg?.secondary ?? {};
 
-  // GIAS OfficialSixthForm flag; missing (pipeline not yet re-run) => false.
-  const hasSixthForm = schoolInfo.has_sixth_form ?? false;
-  const hasFinance = finance != null && finance.per_pupil_spend != null;
-  const hasDeprivation = deprivation != null && deprivation.idaci_decile != null;
-  const hasLocation = schoolInfo.latitude != null && schoolInfo.longitude != null;
-  const hasWellbeing = (latestResults?.sen_support_pct != null || latestResults?.sen_ehcp_pct != null) || hasDeprivation;
-  const p8Suspended = latestResults != null && latestResults.year >= 202425;
-  const hasResults = latestResults?.attainment_8_score != null;
-
-  // Special schools / PRUs / AP sit the same GCSEs but teach pupils with SEND,
-  // so their headline attainment is far below the mainstream average by design.
-  // Drop the England comparison + "below" framing so the page doesn't portray
-  // them as failing against a benchmark that doesn't fit. Attainment 8 is a
-  // single 0–80 score with no subject breakdown to test for a placeholder, so
-  // this keys off establishment type only — a genuine (if extreme) 0.0 at a
-  // mainstream school still shows its real value and comparison.
-  const isSpecial = isSpecialSchool(schoolInfo);
-  const suppressComparison = isSpecial;
-
   const admissionsTag = (() => {
     const policy = schoolInfo.admissions_policy?.toLowerCase() ?? '';
     if (policy.includes('selective')) return 'Selective';
@@ -155,17 +143,9 @@ export function SecondarySchoolDetailView({
   // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [schoolInfo.urn]);
 
-  // Build nav items dynamically based on available data.
-  // Engagement-led order (matches the primary page): recognised Ofsted badge,
-  // then the most-sought sections — results, admissions, history — with the
-  // experience and context sections following.
-  const navItems: { id: string; label: string }[] = [];
-  if (ofsted) navItems.push({ id: 'ofsted', label: 'Ofsted' });
-  if (hasResults) navItems.push({ id: 'gcse', label: 'GCSEs' });
-  if (admissions) navItems.push({ id: 'admissions', label: 'Admissions' });
-  if (yearlyData.length > 1) navItems.push({ id: 'history', label: 'History' });
-  if (hasWellbeing) navItems.push({ id: 'wellbeing', label: 'Wellbeing' });
-  if (hasFinance) navItems.push({ id: 'finances', label: 'Finances' });
+  const navItems = buildSecondaryNavItems(flags, {
+    ofsted, admissions, yearlyDataLength: yearlyData.length,
+  });
 
   // Track active section as user scrolls
   useEffect(() => {

nextjs-app/lib/schoolSections.ts

@@ -0,0 +1,226 @@
+/**
+ * Derived data-shape logic for the school detail pages.
+ *
+ * Pure functions with no React dependency, so the server route can decide
+ * which sections exist without pulling in a client component. Extracted from
+ * SchoolDetailView, which owned this logic inline while it was a client
+ * component.
+ */
+
+import type {
+  School, SchoolResult, AbsenceData, SchoolCensus,
+  OfstedInspection, SchoolAdmissions, SchoolDeprivation, SchoolFinance,
+} from './types';
+import { isSpecialSchool } from './utils';
+
+export interface SchoolFlagsInput {
+  schoolInfo: School;
+  yearlyData: SchoolResult[];
+  absenceData: AbsenceData | null;
+  census: SchoolCensus | null;
+  deprivation: SchoolDeprivation | null;
+  finance: SchoolFinance | null;
+}
+
+export interface SchoolFlags {
+  latestResults: SchoolResult | null;
+  isAllThrough: boolean;
+  isSecondary: boolean;
+  isPrimary: boolean;
+  hasGenderSplit: boolean;
+  hasInclusionData: boolean;
+  hasSchoolLife: boolean;
+  hasDeprivation: boolean;
+  hasFinance: boolean;
+  hasLocation: boolean;
+  hasKS2Results: boolean;
+  hasKS4Results: boolean;
+  hasAnyResults: boolean;
+  isSpecial: boolean;
+  ks2Placeholder: boolean;
+  suppressKs2Comparison: boolean;
+  suppressKs4Comparison: boolean;
+}
+
+export interface NavItem {
+  id: string;
+  label: string;
+}
+
+export function computeSchoolFlags({
+  schoolInfo, yearlyData, absenceData, census, deprivation, finance,
+}: SchoolFlagsInput): SchoolFlags {
+  const latestResults = yearlyData.length > 0 ? yearlyData[yearlyData.length - 1] : null;
+
+  // Phase detection. All-through schools cover BOTH key stages, so they are
+  // neither "pure primary" nor "pure secondary": isSecondary stays true (they
+  // have KS4 data) but isAllThrough gates the primary-only content (KS2 SATs,
+  // KS2 trend) back on and switches phase-specific copy to an all-ages framing.
+  const phase = schoolInfo.phase ?? '';
+  const isAllThrough = phase.toLowerCase() === 'all-through';
+  const isSecondary = phase.toLowerCase().includes('secondary') || isAllThrough;
+  const isPrimary = !isSecondary;
+
+  // Gender split availability (only meaningful for Mixed schools with census data)
+  const isMixedSchool = schoolInfo.gender === 'Mixed' || schoolInfo.gender == null;
+  const hasGenderSplit = !!(isMixedSchool
+    && census?.female_pupils != null
+    && census?.male_pupils != null
+    && (census.female_pupils + census.male_pupils) > 0);
+
+  // Guard for Pupils & Inclusion — only show if at least one metric is available
+  const hasInclusionData = (latestResults?.disadvantaged_pct != null)
+    || (latestResults?.eal_pct != null)
+    || (latestResults?.sen_support_pct != null)
+    || hasGenderSplit;
+
+  const hasSchoolLife = absenceData != null;
+  const hasDeprivation = deprivation != null && deprivation.idaci_decile != null;
+  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;
+
+  // Special schools / PRUs / AP: their pupils sit the same tests but very few
+  // reach the mainstream "expected standard", so a 0% headline and an England
+  // comparison portray them as failing against a benchmark that doesn't fit.
+  const isSpecial = isSpecialSchool(schoolInfo);
+  // Belt-and-braces for KS2: a whole-row zero attainment (every subject 0 — a
+  // special/suppressed signature) is a placeholder, not a real result. This
+  // needs ALL of RWM + reading + writing + maths to be 0, so a genuine 0%
+  // combined (some pupils met individual subjects but not all three) stays
+  // comparable. Attainment 8 is a single 0–80 score with no subject breakdown
+  // to form such a signature, so KS4 keys off establishment type only — a
+  // genuine (if extreme) 0.0 still shows its real figure and comparison.
+  const ks2Placeholder = latestResults != null
+    && latestResults.rwm_expected_pct === 0
+    && (latestResults.reading_expected_pct ?? 0) === 0
+    && (latestResults.writing_expected_pct ?? 0) === 0
+    && (latestResults.maths_expected_pct ?? 0) === 0;
+  // Whether to drop the England-average deltas / national markers / "below"
+  // framing on the attainment measures.
+  const suppressKs2Comparison = isSpecial || ks2Placeholder;
+  const suppressKs4Comparison = isSpecial;
+
+  return {
+    latestResults,
+    isAllThrough, isSecondary, isPrimary,
+    hasGenderSplit, hasInclusionData, hasSchoolLife,
+    hasDeprivation, hasFinance, hasLocation,
+    hasKS2Results, hasKS4Results, hasAnyResults,
+    isSpecial, ks2Placeholder,
+    suppressKs2Comparison, suppressKs4Comparison,
+  };
+}
+
+export interface NavItemsInput {
+  ofsted: OfstedInspection | null;
+  admissions: SchoolAdmissions | null;
+  yearlyDataLength: number;
+}
+
+/**
+ * Build section nav items dynamically — only sections with data.
+ * Order is engagement-led (from section_nav_used analytics): the most-sought
+ * sections — results, admissions, inclusion, history — sit near the top,
+ * after the recognised Ofsted badge; low-demand context sections stay last.
+ *
+ * These conditions MUST match the conditions the section composers use to
+ * render, or the nav will link to sections that do not exist.
+ */
+export function buildNavItems(
+  flags: SchoolFlags,
+  { ofsted, admissions, yearlyDataLength }: NavItemsInput,
+): NavItem[] {
+  const navItems: NavItem[] = [];
+  if (ofsted) navItems.push({ id: 'ofsted', label: 'Ofsted' });
+  if (flags.hasAnyResults) {
+    navItems.push({
+      id: 'results',
+      label: flags.isAllThrough ? 'Results' : flags.isSecondary ? 'GCSEs' : 'SATs',
+    });
+  }
+  if (admissions) navItems.push({ id: 'admissions', label: 'Admissions' });
+  if (flags.hasInclusionData) navItems.push({ id: 'inclusion', label: 'Pupils' });
+  if (yearlyDataLength > 0) navItems.push({ id: 'history', label: 'History' });
+  if (flags.hasSchoolLife) navItems.push({ id: 'school-life', label: 'School Life' });
+  if (flags.hasDeprivation) navItems.push({ id: 'local-area', label: 'Local Area' });
+  if (flags.hasFinance) navItems.push({ id: 'finances', label: 'Finances' });
+  return navItems;
+}
+
+// ---------------------------------------------------------------------------
+// Secondary pages
+//
+// The secondary view is not a variant of the primary one: it has its own
+// section ids ('gcse', 'wellbeing'), its own flags, and gates History on
+// MORE THAN ONE year rather than at least one. Kept as separate functions so
+// neither phase's behaviour bends to accommodate the other.
+// ---------------------------------------------------------------------------
+
+export interface SecondaryFlags {
+  latestResults: SchoolResult | null;
+  hasSixthForm: boolean;
+  hasFinance: boolean;
+  hasDeprivation: boolean;
+  hasLocation: boolean;
+  hasWellbeing: boolean;
+  hasResults: boolean;
+  /** Progress 8 was suspended from the 2024/25 cohort onwards. */
+  p8Suspended: boolean;
+  isSpecial: boolean;
+  suppressComparison: boolean;
+}
+
+export function computeSecondaryFlags({
+  schoolInfo, yearlyData, deprivation, finance,
+}: Omit<SchoolFlagsInput, 'absenceData' | 'census'>): SecondaryFlags {
+  const latestResults = yearlyData.length > 0 ? yearlyData[yearlyData.length - 1] : null;
+
+  // GIAS OfficialSixthForm flag; missing (pipeline not yet re-run) => false.
+  const hasSixthForm = schoolInfo.has_sixth_form ?? false;
+  const hasFinance = finance != null && finance.per_pupil_spend != null;
+  const hasDeprivation = deprivation != null && deprivation.idaci_decile != null;
+  const hasLocation = schoolInfo.latitude != null && schoolInfo.longitude != null;
+  const hasWellbeing = (latestResults?.sen_support_pct != null || latestResults?.sen_ehcp_pct != null) || hasDeprivation;
+  const p8Suspended = latestResults != null && latestResults.year >= 202425;
+  const hasResults = latestResults?.attainment_8_score != null;
+
+  // Special schools / PRUs / AP sit the same GCSEs but teach pupils with SEND,
+  // so their headline attainment is far below the mainstream average by design.
+  // Drop the England comparison + "below" framing so the page doesn't portray
+  // them as failing against a benchmark that doesn't fit. Attainment 8 is a
+  // single 0–80 score with no subject breakdown to test for a placeholder, so
+  // this keys off establishment type only — a genuine (if extreme) 0.0 at a
+  // mainstream school still shows its real value and comparison.
+  const isSpecial = isSpecialSchool(schoolInfo);
+  const suppressComparison = isSpecial;
+
+  return {
+    latestResults, hasSixthForm, hasFinance, hasDeprivation, hasLocation,
+    hasWellbeing, hasResults: !!hasResults, p8Suspended, isSpecial, suppressComparison,
+  };
+}
+
+/**
+ * Build nav items for a secondary page.
+ * Engagement-led order (matches the primary page): recognised Ofsted badge,
+ * then the most-sought sections — results, admissions, history — with the
+ * experience and context sections following.
+ */
+export function buildSecondaryNavItems(
+  flags: SecondaryFlags,
+  { ofsted, admissions, yearlyDataLength }: NavItemsInput,
+): NavItem[] {
+  const navItems: NavItem[] = [];
+  if (ofsted) navItems.push({ id: 'ofsted', label: 'Ofsted' });
+  if (flags.hasResults) navItems.push({ id: 'gcse', label: 'GCSEs' });
+  if (admissions) navItems.push({ id: 'admissions', label: 'Admissions' });
+  if (yearlyDataLength > 1) navItems.push({ id: 'history', label: 'History' });
+  if (flags.hasWellbeing) navItems.push({ id: 'wellbeing', label: 'Wellbeing' });
+  if (flags.hasFinance) navItems.push({ id: 'finances', label: 'Finances' });
+  return navItems;
+}