feat(api): drive has_sixth_form filter and payloads from GIAS flag

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

backend/app.py

@@ -416,10 +416,14 @@ async def get_schools(
         df_latest = df_latest[df_latest["gender"].str.lower() == gender.lower()]
     if admissions_policy:
         df_latest = df_latest[df_latest["admissions_policy"].str.lower() == admissions_policy.lower()]
-    if has_sixth_form == "yes":
-        df_latest = df_latest[df_latest["age_range"].str.contains("18", na=False)]
-    elif has_sixth_form == "no":
-        df_latest = df_latest[~df_latest["age_range"].str.contains("18", na=False)]
+    # GIAS OfficialSixthForm flag (dim_school.has_sixth_form). NULL (flag not
+    # yet populated by the pipeline) is treated as "no sixth form".
+    if has_sixth_form in ("yes", "no"):
+        if "has_sixth_form" in df_latest.columns:
+            flag = df_latest["has_sixth_form"].eq(True)
+        else:  # DB predates the pipeline re-run — fall back to age range
+            flag = df_latest["age_range"].str.contains("18", na=False)
+        df_latest = df_latest[flag if has_sixth_form == "yes" else ~flag]
 
     # Include key result metrics for display on cards
     location_cols = ["latitude", "longitude"]
@@ -596,6 +600,7 @@ async def get_school_details(request: Request, urn: int):
             "address": latest.get("address", ""),
             "religious_denomination": latest.get("religious_denomination", ""),
             "age_range": latest.get("age_range", ""),
+            "has_sixth_form": latest.get("has_sixth_form"),
             "latitude": latest.get("latitude"),
             "longitude": latest.get("longitude"),
             "phase": latest.get("phase"),

backend/data_loader.py

@@ -125,6 +125,7 @@ _MAIN_QUERY = text("""
         s.religious_character  AS religious_denomination,
         s.gender,
         s.age_range,
+        s.has_sixth_form,
         s.admissions_policy,
         s.capacity,
         s.total_pupils         AS gias_total_pupils,

backend/schemas.py

@@ -543,6 +543,7 @@ SCHOOL_COLUMNS = [
     "postcode",
     "religious_denomination",
     "age_range",
+    "has_sixth_form",
     "gender",
     "admissions_policy",
     "ofsted_grade",

backend/tests/test_sixth_form_flag.py

@@ -0,0 +1,97 @@
+"""Tests for the GIAS-driven has_sixth_form flag (spec 2026-07-07 §3).
+
+The filter and payloads must use dim_school.has_sixth_form, not the old
+age_range-contains-"18" substring heuristic. The key regression case is a
+16-19 sixth-form college: flag true, but "16-19" contains no "18".
+"""
+
+import numpy as np
+import pandas as pd
+import pytest
+from fastapi.testclient import TestClient
+
+
+def _schools_df() -> pd.DataFrame:
+    """Latest-year snapshot rows as produced by load_latest_school_data."""
+    base = {
+        "local_authority": "Testshire",
+        "school_type": "Academy",
+        "phase": "Secondary",
+        "address": "1 Test Street",
+        "town": "Testtown",
+        "postcode": "TS1 1AA",
+        "religious_denomination": 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": 1000,
+        "rwm_expected_pct": np.nan,
+        "attainment_8_score": 50.0,
+    }
+    return pd.DataFrame(
+        [
+            # 11-18 school WITH a registered sixth form
+            {**base, "urn": 100001, "school_name": "Alpha High",
+             "age_range": "11-18", "has_sixth_form": True},
+            # 16-19 college: old heuristic said NO ("16-19" has no "18"),
+            # GIAS flag says YES — must appear in the yes-filter results
+            {**base, "urn": 100002, "school_name": "Beta Sixth Form College",
+             "age_range": "16-19", "has_sixth_form": True},
+            # 11-18 age range on paper but NO registered sixth form:
+            # old heuristic said YES, GIAS flag says NO
+            {**base, "urn": 100003, "school_name": "Gamma Academy",
+             "age_range": "11-18", "has_sixth_form": False},
+            # Missing flag (pipeline not yet re-run) — must not crash,
+            # must not match the yes-filter
+            {**base, "urn": 100004, "school_name": "Delta School",
+             "age_range": "11-16", "has_sixth_form": None},
+        ]
+    )
+
+
+@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, "get_supplementary_data", lambda db, urn: {})
+    return TestClient(app_module.app, raise_server_exceptions=False)
+
+
+def _urns(resp):
+    return sorted(s["urn"] for s in resp.json()["schools"])
+
+
+def test_filter_yes_uses_flag_not_age_range(client):
+    resp = client.get("/api/schools?has_sixth_form=yes")
+    assert resp.status_code == 200, resp.text
+    # 16-19 college included; 11-18-without-sixth-form excluded
+    assert _urns(resp) == [100001, 100002]
+
+
+def test_filter_no_uses_flag_not_age_range(client):
+    resp = client.get("/api/schools?has_sixth_form=no")
+    assert resp.status_code == 200, resp.text
+    # Gamma (flag false) and Delta (flag missing => not true)
+    assert _urns(resp) == [100003, 100004]
+
+
+def test_list_payload_includes_flag(client):
+    resp = client.get("/api/schools")
+    assert resp.status_code == 200, resp.text
+    by_urn = {s["urn"]: s for s in resp.json()["schools"]}
+    assert by_urn[100002]["has_sixth_form"] is True
+    assert by_urn[100003]["has_sixth_form"] is False
+    assert by_urn[100004]["has_sixth_form"] is None
+
+
+def test_detail_payload_includes_flag(client):
+    resp = client.get("/api/schools/100002")
+    assert resp.status_code == 200, resp.text
+    assert resp.json()["school_info"]["has_sixth_form"] is True