diff --git a/nextjs-app/__tests__/lib/compareLogic.test.ts b/nextjs-app/__tests__/lib/compareLogic.test.ts
new file mode 100644
index 0000000..d181a5d
--- /dev/null
+++ b/nextjs-app/__tests__/lib/compareLogic.test.ts
@@ -0,0 +1,231 @@
+/**
+ * compareLogic encodes the expert-reviewed comprehension rules for the
+ * compare screen: report-card summarisation (safeguarding never counted),
+ * three-regime Ofsted display, one consistent admissions chip metric,
+ * CI-based progress banding, verdict chips and dot-strip geometry.
+ */
+
+import {
+  OFSTED_LEGACY_GRADES,
+  ofstedDisplay,
+  progressBand,
+  rcAreaLabel,
+  stripPositions,
+  summariseAdmissions,
+  summariseReportCard,
+  verdict,
+} from '@/lib/compareLogic';
+import type { OfstedInspection, SchoolAdmissions } from '@/lib/types';
+
+function ofsted(partial: Partial<OfstedInspection>): OfstedInspection {
+  return {
+    framework: null,
+    inspection_date: null,
+    inspection_type: null,
+    overall_effectiveness: null,
+    quality_of_education: null,
+    behaviour_attitudes: null,
+    personal_development: null,
+    leadership_management: null,
+    early_years_provision: null,
+    previous_overall: null,
+    rc_safeguarding_met: null,
+    rc_inclusion: null,
+    rc_curriculum_teaching: null,
+    rc_achievement: null,
+    rc_attendance_behaviour: null,
+    rc_personal_development: null,
+    rc_leadership_governance: null,
+    rc_early_years: null,
+    rc_sixth_form: null,
+    ...partial,
+  };
+}
+
+const REPORT_CARD = {
+  rc_achievement: { code: 2, label: 'Strong standard' },
+  rc_curriculum_teaching: { code: 2, label: 'Strong standard' },
+  rc_personal_development: { code: 2, label: 'Strong standard' },
+  rc_leadership_governance: { code: 2, label: 'Strong standard' },
+  rc_inclusion: { code: 3, label: 'Expected standard' },
+  rc_early_years: { code: 3, label: 'Expected standard' },
+  rc_attendance_behaviour: { code: 4, label: 'Needs attention' },
+};
+
+describe('summariseReportCard', () => {
+  it('counts graded areas best-first and NAMES problem areas', () => {
+    const s = summariseReportCard(
+      ofsted({ report_card: REPORT_CARD, rc_safeguarding_met: true }),
+    );
+    expect(s.counts).toEqual([
+      { label: 'Strong standard', count: 4 },
+      { label: 'Expected standard', count: 2 },
+    ]);
+    expect(s.problems).toEqual([
+      { areaLabel: 'Attendance & behaviour', label: 'Needs attention' },
+    ]);
+    expect(s.safeguarding).toBe('met');
+    expect(s.allClear).toBe(false);
+  });
+
+  it('never counts safeguarding as a graded area', () => {
+    const s = summariseReportCard(
+      ofsted({
+        report_card: { rc_achievement: { code: 3, label: 'Expected standard' } },
+        rc_safeguarding_met: true,
+      }),
+    );
+    const total = s.counts.reduce((n, c) => n + c.count, 0);
+    expect(total).toBe(1);
+  });
+
+  it('is allClear when everything is Expected standard or better and safeguarding met', () => {
+    const s = summariseReportCard(
+      ofsted({
+        report_card: {
+          rc_achievement: { code: 3, label: 'Expected standard' },
+          rc_inclusion: { code: 1, label: 'Exceptional' },
+        },
+        rc_safeguarding_met: true,
+      }),
+    );
+    expect(s.allClear).toBe(true);
+    expect(s.counts[0]).toEqual({ label: 'Exceptional', count: 1 });
+  });
+
+  it('passes labels through from the API — never invents wording', () => {
+    const s = summariseReportCard(
+      ofsted({ report_card: { rc_inclusion: { code: 4, label: 'Needs attention' } } }),
+    );
+    expect(JSON.stringify(s)).not.toContain('Attention needed');
+  });
+});
+
+describe('ofstedDisplay', () => {
+  it('prefers the report card over any legacy grade', () => {
+    const d = ofstedDisplay(
+      ofsted({ overall_effectiveness: 2, report_card: REPORT_CARD }),
+    );
+    expect(d.kind).toBe('report_card');
+  });
+
+  it('distinguishes graded from carried-forward grades', () => {
+    const graded = ofstedDisplay(
+      ofsted({ overall_effectiveness: 1, grade_source: 'graded' }),
+    );
+    expect(graded).toMatchObject({ kind: 'graded', gradeLabel: 'Outstanding', carriedForward: false });
+
+    const carried = ofstedDisplay(
+      ofsted({ overall_effectiveness: 2, grade_source: 'ungraded_carried_forward' }),
+    );
+    expect(carried).toMatchObject({ kind: 'carried_forward', gradeLabel: 'Good', carriedForward: true });
+  });
+
+  it('handles missing data', () => {
+    expect(ofstedDisplay(null).kind).toBe('none');
+    expect(ofstedDisplay(ofsted({})).kind).toBe('none');
+  });
+
+  it('uses the four legacy grade words', () => {
+    expect(OFSTED_LEGACY_GRADES).toEqual({
+      1: 'Outstanding',
+      2: 'Good',
+      3: 'Requires improvement',
+      4: 'Inadequate',
+    });
+  });
+});
+
+describe('rcAreaLabel', () => {
+  it('maps rc keys to the mockups’ area labels', () => {
+    expect(rcAreaLabel('rc_attendance_behaviour')).toBe('Attendance & behaviour');
+    expect(rcAreaLabel('rc_curriculum_teaching')).toBe('Curriculum & teaching');
+    expect(rcAreaLabel('rc_leadership_governance')).toBe('Leadership & governance');
+  });
+});
+
+describe('summariseAdmissions', () => {
+  function admissions(partial: Partial<SchoolAdmissions>): SchoolAdmissions {
+    return {
+      year: 202627,
+      places_offered: null,
+      total_applications: null,
+      first_preference_offer_pct: null,
+      oversubscribed: null,
+      ...partial,
+    };
+  }
+
+  it('97% → good chip with the mockup wording', () => {
+    const s = summariseAdmissions(
+      admissions({ first_preference_offer_pct: 96.98, total_applications: 457, places_offered: 180 }),
+    );
+    expect(s.chip).toEqual({ tone: 'good', text: '97% of first choices offered' });
+    expect(s.interest).toBe('Named on 457 forms · 180 places');
+  });
+
+  it('73% → warn chip "Over 1 in 4 first choices missed out"', () => {
+    const s = summariseAdmissions(admissions({ first_preference_offer_pct: 73.4 }));
+    expect(s.chip).toEqual({ tone: 'warn', text: 'Over 1 in 4 first choices missed out' });
+  });
+
+  it('100% → "All first choices offered"', () => {
+    const s = summariseAdmissions(admissions({ first_preference_offer_pct: 100 }));
+    expect(s.chip).toEqual({ tone: 'good', text: 'All first choices offered' });
+  });
+
+  it('no data → null chip and interest', () => {
+    const s = summariseAdmissions(null);
+    expect(s.chip).toBeNull();
+    expect(s.interest).toBeNull();
+  });
+});
+
+describe('progressBand', () => {
+  it('CI entirely above zero → above', () => {
+    expect(progressBand(1.2, 0.4, 2.0)).toBe('above');
+  });
+  it('CI entirely below zero → below', () => {
+    expect(progressBand(-1.2, -2.0, -0.4)).toBe('below');
+  });
+  it('CI straddling zero → average', () => {
+    expect(progressBand(0.3, -0.5, 1.1)).toBe('average');
+  });
+  it('missing CI → null (no naive thresholding)', () => {
+    expect(progressBand(1.2, null, null)).toBeNull();
+    expect(progressBand(null, null, null)).toBeNull();
+  });
+});
+
+describe('verdict', () => {
+  it('above / close / below with a 2pp tolerance', () => {
+    expect(verdict(87, 62)).toBe('above');
+    expect(verdict(61, 62)).toBe('close');
+    expect(verdict(40, 62)).toBe('below');
+  });
+});
+
+describe('stripPositions', () => {
+  it('maps a custom domain', () => {
+    const pts = stripPositions([106], 100, 120);
+    expect(pts[0].pos).toBe(30);
+  });
+
+  it('flips a colliding label above', () => {
+    const pts = stripPositions([91, 92], 0, 100);
+    const sorted = [...pts].sort((a, b) => a.value - b.value);
+    expect(sorted[0].labelAbove).toBe(false);
+    expect(sorted[1].labelAbove).toBe(true);
+  });
+
+  it('skips nulls and keeps school indices', () => {
+    const pts = stripPositions([50, null, 70], 0, 100);
+    expect(pts).toHaveLength(2);
+    expect(pts.map((p) => p.schoolIndex)).toEqual([0, 2]);
+  });
+
+  it('clamps out-of-domain values', () => {
+    const pts = stripPositions([95], 100, 120);
+    expect(pts[0].pos).toBe(0);
+  });
+});
diff --git a/nextjs-app/lib/compareLogic.ts b/nextjs-app/lib/compareLogic.ts
new file mode 100644
index 0000000..3d4134f
--- /dev/null
+++ b/nextjs-app/lib/compareLogic.ts
@@ -0,0 +1,244 @@
+/**
+ * Comprehension rules for the compare screen, kept pure and unit-tested.
+ *
+ * These encode the expert-review requirements (spec §8 of the compare
+ * redesign): report-card summaries count graded areas only (safeguarding is
+ * a separate binary judgement), problem areas are always NAMED rather than
+ * folded into counts, grade labels pass through from the API (live-sampled
+ * Ofsted vocabulary — never invented here), admissions chips use one
+ * consistent metric, and progress bands follow DfE's confidence-interval
+ * methodology instead of thresholding point estimates.
+ */
+
+import type { OfstedInspection, SchoolAdmissions } from './types';
+
+// ---------------------------------------------------------------------------
+// Verdicts against an anchor (England average or state-school benchmark)
+// ---------------------------------------------------------------------------
+
+export type Verdict = 'above' | 'close' | 'below';
+
+export function verdict(value: number, anchor: number, tolerance = 2): Verdict {
+  if (value >= anchor + tolerance) return 'above';
+  if (value <= anchor - tolerance) return 'below';
+  return 'close';
+}
+
+// ---------------------------------------------------------------------------
+// Ofsted — three regimes, one display model
+// ---------------------------------------------------------------------------
+
+export const OFSTED_LEGACY_GRADES: Record<number, string> = {
+  1: 'Outstanding',
+  2: 'Good',
+  3: 'Requires improvement',
+  4: 'Inadequate',
+};
+
+/** rc_ key → the area label used across the reviewed mockups. */
+const RC_AREA_LABELS: Record<string, string> = {
+  rc_inclusion: 'Inclusion',
+  rc_curriculum_teaching: 'Curriculum & teaching',
+  rc_achievement: 'Achievement',
+  rc_attendance_behaviour: 'Attendance & behaviour',
+  rc_personal_development: 'Personal development',
+  rc_leadership_governance: 'Leadership & governance',
+  rc_early_years: 'Early years',
+  rc_sixth_form: 'Sixth form',
+};
+
+export function rcAreaLabel(key: string): string {
+  return RC_AREA_LABELS[key] ?? key;
+}
+
+export interface ReportCardSummary {
+  /** Graded areas only, grouped by label, best grade first. */
+  counts: Array<{ label: string; count: number }>;
+  /** Areas rated Needs attention / Urgent improvement — always named. */
+  problems: Array<{ areaLabel: string; label: string }>;
+  safeguarding: 'met' | 'not_met' | null;
+  /** True when every graded area is Expected standard or better and
+   * safeguarding is not "not met". */
+  allClear: boolean;
+}
+
+const PROBLEM_CODES = new Set([4, 5]);
+
+export function summariseReportCard(ofsted: OfstedInspection): ReportCardSummary {
+  const entries = Object.entries(ofsted.report_card ?? {});
+  const byCode = new Map<number, { label: string; count: number }>();
+  const problems: ReportCardSummary['problems'] = [];
+
+  for (const [key, entry] of entries) {
+    if (PROBLEM_CODES.has(entry.code)) {
+      problems.push({ areaLabel: rcAreaLabel(key), label: entry.label });
+    } else {
+      const existing = byCode.get(entry.code);
+      if (existing) existing.count += 1;
+      else byCode.set(entry.code, { label: entry.label, count: 1 });
+    }
+  }
+
+  const counts = [...byCode.entries()]
+    .sort(([a], [b]) => a - b)
+    .map(([, v]) => v);
+
+  const safeguarding =
+    ofsted.rc_safeguarding_met === true
+      ? 'met'
+      : ofsted.rc_safeguarding_met === false
+        ? 'not_met'
+        : null;
+
+  return {
+    counts,
+    problems,
+    safeguarding,
+    allClear: entries.length > 0 && problems.length === 0 && safeguarding !== 'not_met',
+  };
+}
+
+export type OfstedDisplay =
+  | { kind: 'none' }
+  | { kind: 'graded'; grade: number; gradeLabel: string; carriedForward: false }
+  | { kind: 'carried_forward'; grade: number; gradeLabel: string; carriedForward: true }
+  | { kind: 'report_card'; summary: ReportCardSummary };
+
+export function ofstedDisplay(
+  ofsted: OfstedInspection | null | undefined,
+): OfstedDisplay {
+  if (!ofsted) return { kind: 'none' };
+
+  // A report card is the newest inspection format; when present it wins —
+  // never derive or prefer an overall grade alongside it.
+  if (ofsted.report_card && Object.keys(ofsted.report_card).length > 0) {
+    return { kind: 'report_card', summary: summariseReportCard(ofsted) };
+  }
+
+  const grade = ofsted.overall_effectiveness;
+  const gradeLabel = grade != null ? OFSTED_LEGACY_GRADES[grade] : undefined;
+  if (grade == null || gradeLabel === undefined) return { kind: 'none' };
+
+  if (ofsted.grade_source === 'ungraded_carried_forward') {
+    return { kind: 'carried_forward', grade, gradeLabel, carriedForward: true };
+  }
+  return { kind: 'graded', grade, gradeLabel, carriedForward: false };
+}
+
+// ---------------------------------------------------------------------------
+// Admissions — one consistent chip metric (first-preference success)
+// ---------------------------------------------------------------------------
+
+export interface AdmissionsSummary {
+  firstPrefPct: number | null;
+  chip: { tone: 'good' | 'warn' | 'neutral'; text: string } | null;
+  /** e.g. "Named on 457 forms · 180 places" — total preferences at any rank,
+   * deliberately not phrased as head-to-head applications. */
+  interest: string | null;
+}
+
+export function summariseAdmissions(
+  a: SchoolAdmissions | null | undefined,
+): AdmissionsSummary {
+  if (!a) return { firstPrefPct: null, chip: null, interest: null };
+
+  const pct =
+    a.first_preference_offer_pct != null
+      ? Math.round(a.first_preference_offer_pct)
+      : null;
+
+  let chip: AdmissionsSummary['chip'] = null;
+  if (pct != null) {
+    if (pct >= 100) {
+      chip = { tone: 'good', text: 'All first choices offered' };
+    } else if (pct < 75) {
+      chip = { tone: 'warn', text: 'Over 1 in 4 first choices missed out' };
+    } else {
+      chip = { tone: pct >= 90 ? 'good' : 'neutral', text: `${pct}% of first choices offered` };
+    }
+  }
+
+  const interest =
+    a.total_applications != null && a.places_offered != null
+      ? `Named on ${a.total_applications.toLocaleString('en-GB')} forms · ${a.places_offered.toLocaleString('en-GB')} places`
+      : null;
+
+  return { firstPrefPct: pct, chip, interest };
+}
+
+// ---------------------------------------------------------------------------
+// Progress bands — DfE confidence-interval methodology
+// ---------------------------------------------------------------------------
+
+export function progressBand(
+  score: number | null,
+  lower: number | null,
+  upper: number | null,
+): 'above' | 'average' | 'below' | null {
+  if (score == null || lower == null || upper == null) return null;
+  if (lower > 0) return 'above';
+  if (upper < 0) return 'below';
+  return 'average';
+}
+
+// ---------------------------------------------------------------------------
+// Dot-strip geometry
+// ---------------------------------------------------------------------------
+
+export interface StripPoint {
+  /** 0–100 percentage position along the track. */
+  pos: number;
+  labelAbove: boolean;
+  value: number;
+  schoolIndex: number;
+}
+
+/** Labels within 4% of the domain of a lower neighbour flip above the strip
+ * (the reviewed mockups' collision nudge). */
+export function stripPositions(
+  values: Array<number | null>,
+  min = 0,
+  max = 100,
+): StripPoint[] {
+  const span = max - min;
+  const points = values
+    .map((value, schoolIndex) => ({ value, schoolIndex }))
+    .filter((p): p is { value: number; schoolIndex: number } => p.value != null)
+    .map((p) => ({
+      value: p.value,
+      schoolIndex: p.schoolIndex,
+      pos: Math.min(100, Math.max(0, ((p.value - min) / span) * 100)),
+      labelAbove: false,
+    }));
+
+  const nudge = span * 0.04;
+  let lastBelow = -Infinity;
+  for (const p of [...points].sort((a, b) => a.value - b.value)) {
+    if (p.value - lastBelow < nudge) {
+      p.labelAbove = true;
+    } else {
+      lastBelow = p.value;
+    }
+  }
+  return points;
+}
+
+// ---------------------------------------------------------------------------
+// Metric extraction
+// ---------------------------------------------------------------------------
+
+/** Latest non-null yearly value of `metricKey` per school, in `urns` order. */
+export function latestValues(
+  data: Record<string, { yearly_data: Array<Record<string, unknown> & { year: number }> }>,
+  urns: number[],
+  metricKey: string,
+): Array<number | null> {
+  return urns.map((urn) => {
+    const rows = data[String(urn)]?.yearly_data ?? [];
+    for (let i = rows.length - 1; i >= 0; i--) {
+      const v = rows[i][metricKey];
+      if (typeof v === 'number' && !Number.isNaN(v)) return v;
+    }
+    return null;
+  });
+}