fix(api): filter by every GIAS phase, not just the grouped ones

/api/schools only recognised primary, secondary and all-through. Any
other phase the search page offers (nursery, 16 plus, middle deemed
primary/secondary) fell through to no filter, so "Nursery" returned the
whole result set, mostly primaries. Ungrouped phases now match exactly,
and an unknown phase returns nothing rather than everything.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

backend/app.py

@@ -736,7 +736,7 @@ 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),
+    phase: Optional[str] = Query(None, description="Filter by phase: primary or secondary (grouped), or any GIAS phase name (exact)", max_length=50),
     postcode: Optional[str] = Query(None, description="Search near postcode", max_length=10),
     radius: float = Query(5.0, ge=0.1, le=5, description="Search radius in miles"),
     page: int = Query(1, ge=1, le=1000, description="Page number"),
@@ -771,11 +771,13 @@ async def get_schools(
 
     # Phase filter — uses PHASE_GROUPS so all-through/middle schools appear
     # in the correct phase(s) rather than being invisible to both filters.
+    # Any other GIAS phase (nursery, 16 plus, middle deemed ...) is an exact
+    # match. It must never fall through to no filter: the search page offers
+    # every phase, and "Nursery" used to return the whole result set.
     if phase:
         phase_lower = phase.lower().replace("_", "-")
-        allowed = PHASE_GROUPS.get(phase_lower)
-        if allowed:
-            df_latest = df_latest[df_latest["phase"].str.lower().isin(allowed)]
+        allowed = PHASE_GROUPS.get(phase_lower, {phase_lower})
+        df_latest = df_latest[df_latest["phase"].fillna("").str.lower().isin(allowed)]
 
     # Secondary-specific filters (after phase filter)
     if gender:

backend/tests/test_phase_filter.py

@@ -0,0 +1,84 @@
+"""The /api/schools phase filter.
+
+The search page offers every GIAS phase, but the filter only knew the three
+grouped ones (primary, secondary, all-through). Anything else — nursery,
+16 plus, the middle-deemed phases — fell through to no filter at all, so
+"Nursery" returned the whole result set, mostly primaries.
+"""
+
+import numpy as np
+import pandas as pd
+import pytest
+from fastapi.testclient import TestClient
+
+PHASES = {
+    100001: "Nursery",
+    100002: "Primary",
+    100003: "Middle deemed primary",
+    100004: "Secondary",
+    100005: "Middle deemed secondary",
+    100006: "16 plus",
+    100007: "All-through",
+}
+
+
+def _schools_df() -> pd.DataFrame:
+    base = {
+        "local_authority": "Testshire",
+        "school_type": "Academy",
+        "address": "1 Test Street",
+        "town": "Testtown",
+        "postcode": "TS1 1AA",
+        "religious_denomination": None,
+        "age_range": "4-11",
+        "has_sixth_form": None,
+        "gender": "Mixed",
+        "admissions_policy": None,
+        "ofsted_grade": np.nan,
+        "ofsted_date": None,
+        "ofsted_framework": None,
+        "latitude": 51.5,
+        "longitude": -0.1,
+        "year": 202425,
+        "total_pupils": 300,
+        "rwm_expected_pct": np.nan,
+        "attainment_8_score": np.nan,
+    }
+    return pd.DataFrame([
+        {**base, "urn": urn, "school_name": f"{phase} School", "phase": phase}
+        for urn, phase in PHASES.items()
+    ])
+
+
+@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)
+    return TestClient(app_module.app, raise_server_exceptions=False)
+
+
+def _urns(client, phase):
+    resp = client.get("/api/schools", params={"phase": phase})
+    assert resp.status_code == 200, resp.text
+    return sorted(s["urn"] for s in resp.json()["schools"])
+
+
+@pytest.mark.parametrize("phase, urn", [
+    ("nursery", 100001),
+    ("16 plus", 100006),
+    ("middle deemed primary", 100003),
+    ("middle deemed secondary", 100005),
+])
+def test_an_ungrouped_phase_matches_exactly(client, phase, urn):
+    assert _urns(client, phase) == [urn]
+
+
+def test_grouped_phases_still_take_in_their_related_phases(client):
+    assert _urns(client, "primary") == [100002, 100003, 100007]
+    assert _urns(client, "secondary") == [100004, 100005, 100006, 100007]
+
+
+def test_an_unknown_phase_returns_nothing_rather_than_everything(client):
+    assert _urns(client, "kindergarten") == []

e2e/tests/journeys.spec.ts

@@ -272,6 +272,31 @@ test('searching by postcode returns nearby schools', async ({ page }) => {
   await expect(schoolLinks(page).first()).toBeVisible({ timeout: 15_000 });
 });
 
+test('the phase filter switches straight from secondary to primary', async ({ page }) => {
+  // The phase options once came from the result set, which the phase filter
+  // had already narrowed — so with secondary chosen, primary was not offered.
+  await page.goto('/?search=school&phase=secondary');
+  const phase = page.getByRole('combobox', { name: 'Phase' });
+  await expect(phase).toHaveValue('secondary', { timeout: 15_000 });
+  await phase.selectOption('primary');
+  await expect(page).toHaveURL(/[?&]phase=primary(&|$)/);
+  await expect(phase).toHaveValue('primary');
+});
+
+test('a phase outside primary/secondary filters to that phase, not to everything', async ({ page }) => {
+  // The search page offers every GIAS phase, but the API only knew the grouped
+  // ones and silently dropped the rest — so "Nursery" returned primaries.
+  for (const phase of ['Nursery', '16 plus']) {
+    const res = await page.request.get(
+      `/api/schools?phase=${encodeURIComponent(phase.toLowerCase())}&page_size=50`);
+    expect(res.ok()).toBeTruthy();
+    const phases = new Set(
+      ((await res.json()).schools ?? []).map((s: { phase?: string }) => s.phase));
+    expect([...phases], `phase=${phase} returned other phases`)
+      .toEqual(phases.size ? [phase] : []);
+  }
+});
+
 test('a report-card school shows a Report Card badge in search results, not its old grade', async ({ page }) => {
   // List/map badges keyed off ofsted_grade (the carried-forward legacy grade)
   // and never reached the report-card branch, so report-card schools were

nextjs-app/__tests__/components/FilterBarPhase.test.tsx

@@ -0,0 +1,40 @@
+import { render, screen, within } from '@testing-library/react';
+import { FilterBar } from '@/components/FilterBar';
+
+let searchParams = new URLSearchParams();
+jest.mock('next/navigation', () => ({
+  useRouter: () => ({ push: jest.fn(), replace: jest.fn(), prefetch: jest.fn() }),
+  usePathname: () => '/',
+  useSearchParams: () => searchParams,
+}));
+
+const FILTERS = {
+  local_authorities: [], school_types: [], years: [],
+  phases: ['Primary', 'Secondary', 'All-through'],
+  genders: [], admissions_policies: [],
+};
+
+/**
+ * The phase options must not come from the result set. The backend scopes its
+ * result filters to the schools it returns, and it applies the phase filter
+ * first — so with "secondary" chosen the scoped list holds only secondary-ish
+ * phases, and switching to primary meant going back to "Any phase" first.
+ */
+describe('FilterBar phase options', () => {
+  it('offers every phase while a phase filter narrows the results', () => {
+    searchParams = new URLSearchParams('search=hampton&phase=secondary');
+    render(
+      <FilterBar
+        filters={FILTERS}
+        resultFilters={{
+          local_authorities: [], school_types: [],
+          phases: ['Secondary', 'All-through'],
+          genders: [], admissions_policies: [],
+        }}
+      />,
+    );
+    const phase = screen.getByRole('combobox', { name: 'Phase' });
+    expect(within(phase).getByRole('option', { name: 'Primary' })).toBeInTheDocument();
+    expect(phase).toHaveValue('secondary');
+  });
+});

nextjs-app/components/FilterBar.tsx

@@ -295,7 +295,10 @@ export function FilterBar({
   const laOptions =
     resultFilters?.local_authorities ?? filters.local_authorities;
   const typeOptions = resultFilters?.school_types ?? filters.school_types;
-  const phaseOptions = resultFilters?.phases ?? filters.phases ?? [];
+  // Phase is the exception: always the full list. The result set has already
+  // been narrowed by the phase filter, so scoping to it would leave only the
+  // chosen phase on offer and switching phase would need "Any phase" first.
+  const phaseOptions = filters.phases ?? [];
   const genderOptions = resultFilters?.genders ?? filters.genders ?? [];
   const admissionsPolicyOptions =
     resultFilters?.admissions_policies ?? filters.admissions_policies ?? [];