diff --git a/e2e/tests/journeys.spec.ts b/e2e/tests/journeys.spec.ts
index 2d1f881..1586b4f 100644
--- a/e2e/tests/journeys.spec.ts
+++ b/e2e/tests/journeys.spec.ts
@@ -272,6 +272,17 @@ 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 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
diff --git a/nextjs-app/__tests__/components/FilterBarPhase.test.tsx b/nextjs-app/__tests__/components/FilterBarPhase.test.tsx
new file mode 100644
index 0000000..ddbed2e
--- /dev/null
+++ b/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');
+  });
+});
diff --git a/nextjs-app/components/FilterBar.tsx b/nextjs-app/components/FilterBar.tsx
index 20f7dbf..c08211d 100644
--- a/nextjs-app/components/FilterBar.tsx
+++ b/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 ?? [];