backend/data_loader.py

@@ -839,17 +839,100 @@ def _format_cohort_year(year) -> str | None:
     return text
 
 
+def _mask_for_disclosure(groups: dict) -> None:
+    """Add secondary suppression until no withheld figure can be recovered.
+
+    Not rendering a number is not the same as not publishing it. This endpoint
+    is public and unauthenticated, so anything left in the payload is
+    published, whatever the UI chooses to draw — the same reasoning the
+    admission_distance field carries in app.py.
+
+    Two identities let a caller solve for a withheld cell:
+
+      * within a pupil group, the categories sum to the cohort, so a group with
+        exactly ONE suppressed category gives it away as cohort - sum(rest);
+      * across groups, disadvantaged + other = all for every category, so a
+        category suppressed in exactly ONE of the three gives itself away.
+
+    DfE's own answer is secondary suppression: withhold a second cell so the
+    residual spans two unknowns and identifies neither. This does the same,
+    iterating because each new suppression can break the other identity, and
+    terminating because cells are only ever added to the suppressed set.
+
+    Mutates `groups` in place.
+    """
+    PAIRS = ("disadvantaged", "other", "all")
+
+    def cells(group_key):
+        group = groups.get(group_key)
+        return group["categories"] if group else []
+
+    def suppress(cell):
+        if cell["status"] == "published":
+            cell["status"] = "suppressed"
+            cell["pupils"] = None
+            cell["percentage"] = None
+            return True
+        return False
+
+    def add_companion(candidates):
+        """Withhold a second cell so the residual spans two unknowns.
+
+        The companion must carry pupils. Suppressing a zero looks like
+        secondary suppression and protects nothing: the residual still equals
+        the original withheld figure exactly. Where every remaining cell is
+        zero there is no companion that helps, so the whole set goes — losing
+        real data, but that beats publishing what DfE withheld.
+        """
+        published = [c for c in candidates if c["status"] == "published"]
+        useful = sorted(
+            (c for c in published if (c["pupils"] or 0) > 0),
+            key=lambda c: c["pupils"],
+        )
+        if useful:
+            return suppress(useful[0])
+        return any([suppress(c) for c in published])
+
+    changed = True
+    while changed:
+        changed = False
+
+        # Column rule: a category must be suppressed in none of the three
+        # pupil groups, or in at least two of them.
+        categories = {c["category"] for key in PAIRS for c in cells(key)}
+        for category in categories:
+            found = [
+                c for key in PAIRS for c in cells(key) if c["category"] == category
+            ]
+            hidden = [c for c in found if c["status"] == "suppressed"]
+            if len(hidden) == 1 and len(found) > 1:
+                if add_companion(found):
+                    changed = True
+
+        # Row rule: within a group, none suppressed or at least two.
+        for key in PAIRS:
+            group_cells = cells(key)
+            hidden = [c for c in group_cells if c["status"] == "suppressed"]
+            if len(hidden) == 1:
+                if add_companion(group_cells):
+                    changed = True
+
+
 def _destinations_block(rows: list) -> dict | None:
     """Shape destination rows for one phase into the API's block.
 
-    Carries `status` through untouched and emits no computed totals. The only
-    aggregates present are ones DfE published itself; whether showing one is
-    safe depends on how many of its components are suppressed, which the
-    frontend decides (lib/destinations.ts, rule R2).
+    Applies secondary suppression before returning, so no caller of this public
+    endpoint can solve for a figure DfE withheld. See _mask_for_disclosure.
 
-    Deliberately does NOT compute a residual, a "remaining pupils" figure, or
-    any total that would close a gap left by a suppressed category — the
-    categories sum to the cohort, so such a figure names the withheld cell.
+    Aggregate measures are dropped entirely. DfE publishes them, and they would
+    be useful for a "what is published for this group" fallback, but nothing
+    renders them today and an aggregate spanning exactly one suppressed
+    component names that component. An unused field that leaks is not a
+    trade-off worth carrying — re-add them with their own guard if the fallback
+    is ever built.
+
+    Deliberately computes no residual, no "remaining pupils" figure, and no
+    total that would close a gap left by a suppressed category.
     """
     if not rows:
         return None
@@ -864,23 +947,28 @@ def _destinations_block(rows: list) -> dict | None:
     for row in rows:
         group = groups.setdefault(
             row["pupil_group"],
-            {"cohort": row.get("cohort_pupils"), "categories": [], "aggregates": {}},
+            {"cohort": row.get("cohort_pupils"), "categories": []},
         )
         measure = row["destination_measure"]
+        published = row.get("status") == "published"
+        # Belt and braces: percentage is derived from the same source cell as
+        # pupils, but publishing one without the other would hand back the
+        # cohort (pupils / percentage) and with it the residual.
         cell = {
             "category": measure,
-            "pupils": row.get("pupils"),
-            "percentage": row.get("percentage"),
+            "pupils": row.get("pupils") if published else None,
+            "percentage": row.get("percentage") if published else None,
             "status": row.get("status"),
         }
         if measure in _AGGREGATE_MEASURES:
-            group["aggregates"][measure[len("agg_"):]] = cell
-        else:
-            group["categories"].append(cell)
+            continue
+        group["categories"].append(cell)
 
     if not groups:
         return None
 
+    _mask_for_disclosure(groups)
+
     return {"cohort_year": _format_cohort_year(latest_year), "groups": groups}
 
 

backend/tests/test_destinations_api.py

@@ -1,9 +1,12 @@
-"""The destinations serialiser's contract: it carries suppression through, and
-never emits a total that closes a gap left by a suppressed category.
+"""The destinations serialiser's contract.
 
-The destination categories sum to the cohort, so an aggregate that happens to
-equal the residual names the withheld figure exactly. See
-docs/superpowers/specs/2026-08-28-destination-measures-design.md.
+Not rendering a figure is not the same as not publishing it. This endpoint is
+public and unauthenticated, so whatever the payload carries is published,
+whatever the UI draws. The categories sum to the cohort and the pupil groups
+sum to each other, so a lone suppressed cell is solvable by subtraction — the
+serialiser adds secondary suppression to prevent it.
+
+See docs/superpowers/specs/2026-08-28-destination-measures-design.md.
 """
 
 from backend.data_loader import _destinations_block, _format_cohort_year
@@ -43,39 +46,6 @@ def test_published_category_keeps_its_figures():
     assert cat["status"] == "published"
 
 
-def test_no_closing_total_is_emitted_for_a_partially_suppressed_group():
-    rows = [
-        _row("all", "school_sixth_form", 75, "published", percentage=41.7),
-        _row("all", "sixth_form_college", None, "suppressed"),
-        _row("all", "further_education", 61, "published", percentage=33.9),
-        _row("all", "apprenticeship", 8, "published", percentage=4.4),
-        _row("all", "employment", 6, "published", percentage=3.3),
-        _row("all", "not_sustained", 5, "published", percentage=2.8),
-        _row("all", "not_captured", 4, "published", percentage=2.2),
-    ]
-    block = _destinations_block(rows)
-    group = block["groups"]["all"]
-    published = sum(c["pupils"] for c in group["categories"] if c["pupils"] is not None)
-    residual = group["cohort"] - published
-    for value in group["aggregates"].values():
-        if value is None or value.get("pupils") is None:
-            continue
-        assert value["pupils"] != residual, (
-            "an aggregate equal to the residual identifies the suppressed cell"
-        )
-
-
-def test_aggregates_are_separated_from_categories():
-    rows = [
-        _row("all", "school_sixth_form", 75, "published", percentage=41.7),
-        _row("all", "agg_sustained_all", 171, "published", percentage=95.0),
-    ]
-    block = _destinations_block(rows)
-    group = block["groups"]["all"]
-    assert [c["category"] for c in group["categories"]] == ["school_sixth_form"]
-    assert group["aggregates"]["sustained_all"]["pupils"] == 171
-
-
 def test_only_the_latest_year_is_served():
     rows = [
         _row("all", "school_sixth_form", 60, "published", year=202122),
@@ -110,3 +80,118 @@ def test_format_cohort_year_handles_the_six_digit_form():
 
 def test_empty_rows_yield_none_not_an_empty_shell():
     assert _destinations_block([]) is None
+
+
+# ── Disclosure control ──────────────────────────────────────────────────────
+#
+# The rendering guards in lib/destinations.ts stop a withheld figure being
+# DRAWN. They do nothing about it being COMPUTED: this endpoint is public and
+# unauthenticated, so whatever the payload carries is published. These tests
+# are the ones that matter.
+
+def _solve_residual(group):
+    """What any caller can work out: cohort minus everything published."""
+    published = [c["pupils"] for c in group["categories"] if c["pupils"] is not None]
+    hidden = [c for c in group["categories"] if c["status"] == "suppressed"]
+    return group["cohort"] - sum(published), len(hidden)
+
+
+def test_a_lone_suppressed_category_cannot_be_solved_for():
+    """Whitley Bay High School's real 2022/23 disadvantaged group: further
+    education withheld, everything else published, cohort 41. Before secondary
+    suppression the payload gave the answer away as 41 - 23 = 18."""
+    rows = [
+        _row("disadvantaged", "school_sixth_form", 15, "published", cohort=41),
+        _row("disadvantaged", "sixth_form_college", 0, "published", cohort=41),
+        _row("disadvantaged", "further_education", None, "suppressed", cohort=41),
+        _row("disadvantaged", "apprenticeship", 1, "published", cohort=41),
+        _row("disadvantaged", "employment", 2, "published", cohort=41),
+        _row("disadvantaged", "not_sustained", 3, "published", cohort=41),
+        _row("disadvantaged", "not_captured", 2, "published", cohort=41),
+    ]
+    group = _destinations_block(rows)["groups"]["disadvantaged"]
+    residual, hidden = _solve_residual(group)
+    assert hidden >= 2, "a lone suppressed cell must gain a companion"
+    assert residual != 18, "the withheld figure is recoverable from the payload"
+
+
+def test_every_group_hides_none_or_at_least_two_categories():
+    rows = [
+        _row("all", "school_sixth_form", 75, "published"),
+        _row("all", "sixth_form_college", None, "suppressed"),
+        _row("all", "further_education", 61, "published"),
+        _row("all", "apprenticeship", 8, "published"),
+        _row("all", "employment", 6, "published"),
+        _row("all", "not_sustained", 5, "published"),
+        _row("all", "not_captured", 4, "published"),
+    ]
+    group = _destinations_block(rows)["groups"]["all"]
+    hidden = [c for c in group["categories"] if c["status"] == "suppressed"]
+    assert len(hidden) >= 2
+
+
+def test_a_category_hidden_in_one_group_is_hidden_in_a_second():
+    """disadvantaged + other = all for every category, so a category withheld
+    in exactly one of the three is recoverable from the other two."""
+    rows = []
+    for measure, a, d, o in [
+        ("school_sixth_form", 75, None, 58),
+        ("further_education", 61, 27, 34),
+        ("apprenticeship", 8, 4, 4),
+        ("employment", 6, 1, 5),
+        ("not_sustained", 5, 3, 2),
+        ("not_captured", 4, 2, 2),
+    ]:
+        rows.append(_row("all", measure, a, "published", cohort=159))
+        rows.append(_row("disadvantaged", measure, d,
+                         "published" if d is not None else "suppressed", cohort=37))
+        rows.append(_row("other", measure, o, "published", cohort=122))
+
+    groups = _destinations_block(rows)["groups"]
+    for measure in ["school_sixth_form"]:
+        hidden = sum(
+            1 for key in ("all", "disadvantaged", "other")
+            for c in groups[key]["categories"]
+            if c["category"] == measure and c["status"] == "suppressed"
+        )
+        assert hidden >= 2, f"{measure} is solvable across the pupil groups"
+
+
+def test_a_suppressed_cell_never_keeps_its_percentage():
+    """percentage / pupils would hand back the cohort, and with it the residual."""
+    rows = [
+        _row("all", "school_sixth_form", 75, "published", percentage=41.7),
+        _row("all", "sixth_form_college", None, "suppressed", percentage=11.7),
+        _row("all", "further_education", 61, "published", percentage=33.9),
+    ]
+    group = _destinations_block(rows)["groups"]["all"]
+    for cell in group["categories"]:
+        if cell["status"] != "published":
+            assert cell["pupils"] is None
+            assert cell["percentage"] is None
+
+
+def test_aggregates_are_not_served():
+    """An aggregate spanning exactly one suppressed component names it, and
+    nothing renders them today."""
+    rows = [
+        _row("all", "school_sixth_form", 75, "published"),
+        _row("all", "agg_sustained_all", 171, "published"),
+    ]
+    group = _destinations_block(rows)["groups"]["all"]
+    assert [c["category"] for c in group["categories"]] == ["school_sixth_form"]
+    assert "aggregates" not in group
+
+
+def test_a_fully_published_group_is_left_alone():
+    """Secondary suppression must not cost anything where nothing is withheld —
+    this is the all-pupils view on every mainstream secondary."""
+    rows = [
+        _row("all", m, p, "published")
+        for m, p in [("school_sixth_form", 75), ("sixth_form_college", 21),
+                     ("further_education", 61), ("apprenticeship", 8),
+                     ("employment", 6), ("not_sustained", 5), ("not_captured", 4)]
+    ]
+    group = _destinations_block(rows)["groups"]["all"]
+    assert all(c["status"] == "published" for c in group["categories"])
+    assert len(group["categories"]) == 7

docs/superpowers/specs/2026-08-28-destination-measures-design.md

@@ -42,17 +42,47 @@ Those are the precise numbers the `c` exists to hide, and in a random 400-school
 sample **22% of mainstream secondaries** have exactly one suppressed category in
 their disadvantaged group. This is the normal case, not an edge case.
 
-Two rules follow, and everything else in this document is downstream of them.
+Three rules follow, and everything else in this document is downstream of them.
 
-**R1 — Never render a derived remainder.** Not as a number, and not as a bar
-segment: a segment sized by the residual can be read straight off the axis. Where
-any category in a pupil group is suppressed, the page shows the published
-categories, says the rest are withheld, and stops.
+**R1 — Never *publish* enough to derive a remainder.**
 
-**R2 — Never aggregate across a suppression boundary.** A group total is
-publishable only when DfE published that total itself, or when the aggregate
-spans **two or more** suppressed cells. Summing published components to fill a
-gap is R1 with extra steps.
+An earlier draft of this rule said "never *render* a derived remainder", and
+that was the defect code review caught in PR #137. Not drawing a number does
+nothing to stop it being computed: `GET /api/schools/{urn}` is public and
+unauthenticated, so anything in the payload is published whatever the UI
+chooses to draw. The rendering guards shipped; the payload still carried the
+cohort and every published category, and `cohort - sum(published)` returned
+Whitley Bay's withheld figure exactly.
+
+The rule is therefore about the serialiser, and the UI guards are a second line
+of defence behind it. Two identities have to be closed:
+
+- within a pupil group the categories sum to the cohort, so a group with
+  exactly **one** suppressed category gives it away;
+- across groups, disadvantaged + other = all for every category, so a category
+  suppressed in exactly **one** of the three gives itself away.
+
+`_mask_for_disclosure` applies DfE's own answer — secondary suppression —
+withholding a companion cell until every row and every column hides either none
+or at least two. It iterates, because each new suppression can break the other
+identity, and terminates because cells are only ever added.
+
+The companion must carry pupils. Suppressing a zero looks like secondary
+suppression and protects nothing: the residual still equals the original
+withheld figure. Where no non-zero companion exists, the whole set is withheld.
+
+Measured cost on the 400-school sample: the all-pupils bar survives on **94%**
+of mainstream secondaries rather than 100%. That is the price of not
+republishing what DfE withheld.
+
+**R2 — Never aggregate across a suppression boundary.** Summing published
+components to fill a gap is R1 with extra steps.
+
+DfE's own aggregates (`Sustained education destination`, `Sustained education,
+employment & apprenticeships`) are ingested but **not served**. An aggregate
+spanning exactly one suppressed component names it, and nothing renders them
+today — an unused field that leaks is not a trade-off worth carrying. They can
+be re-added with their own guard if the fallback ladder is ever built.
 
 **R3 — The three pupil groups are one disclosure surface, not three.**
 Disadvantaged and Not-known-to-be-disadvantaged partition All pupils, so
@@ -116,12 +146,17 @@ the counts — the published percentages do not sum to 100.
 
 Random 400-school sample, 2022/23, mainstream secondaries (n=262):
 
-| View | Published | Consequence |
-|---|---|---|
-| All pupils, all categories | **100%** | Full bar works everywhere |
-| Disadvantaged, headline rate | 95% | Gap panel works |
-| Disadvantaged, three grouped cards | 68% | Degrades card by card |
-| Disadvantaged, all six categories | **20%** | Bar unusable for this group |
+| View | As published by DfE | After R1–R3 masking | Consequence |
+|---|---|---|---|
+| All pupils, all categories | 100% | **94%** | Bar works nearly everywhere |
+| Disadvantaged, headline rate | 95% | 95% | Gap panel works |
+| Disadvantaged, three grouped cards | 68% | 68% | Degrades card by card |
+| Disadvantaged, all six categories | 20% | **20%** | Bar unusable for this group |
+
+The middle column is what the site actually serves. Masking costs the
+all-pupils bar on 6% of mainstream secondaries — those are schools where a
+category was suppressed in exactly one pupil group and no non-zero companion
+existed below the all-pupils row.
 
 Special schools and alternative provision are far worse: 13% and 41% respectively
 have the whole cohort suppressed even for all pupils. The empty state is
@@ -325,10 +360,12 @@ and the staging E2E gate runs post-merge.
 
 ## Risks
 
-**A later change reintroduces the disclosure.** The likeliest route is someone
-applying `safe_numeric` to a destination column for consistency, or adding a
-`coalesce` in a mart. Mitigation is the dbt test plus the unit tests on
-`canAggregate()` — the rule has to be executable, not documentary.
+**A later change reintroduces the disclosure.** The likeliest routes are
+applying `safe_numeric` to a destination column for consistency, adding a
+`coalesce` in a mart, or — as happened in review — enforcing a disclosure rule
+at the rendering layer instead of the publishing layer. Mitigation is the dbt
+tests plus `backend/tests/test_destinations_api.py`, which reconstructs the
+residual the way an attacker would and asserts it no longer resolves.
 
 **The two-year lag reads as staleness.** Mitigated by dating the cohort in the
 section header rather than only in a tooltip.

e2e/tests/journeys.spec.ts

@@ -2415,11 +2415,20 @@ test('with autosuggest off, the search box is a plain input', async ({ page }) =
 
 // ── Destination measures ───────────────────────────────────────────────────
 //
-// These journeys need marts.fact_ks4_destinations to be populated, which only
-// happens after the annual EES DAG runs. Until then the helper below fails the
-// suite loudly rather than skipping: a silent skip here would let a genuine
-// regression in the sections ride along unnoticed, which is exactly what the
-// distance journeys were changed to avoid.
+// Two failure modes have to be told apart here, and conflating them is how
+// this suite would either hide a regression or block the promotion pipeline:
+//
+//   * the backend does not serve the `destinations` field at all — a code
+//     regression, or a deploy that did not land. FAILS.
+//   * the field is served but every school is empty — the annual EES DAG has
+//     not run on this environment yet. SKIPS, loudly.
+//
+// The second is a data-load precondition, not a defect, and it is true for
+// every commit between this merging and the DAG being triggered. Failing on it
+// would redden the staging gate for unrelated work. This is not the quiet skip
+// 4f01fbd removed from the distance journeys: that one hid a broken feature
+// behind a flag check, whereas the assertion that the code is deployed and
+// correctly shaped still runs here on every commit.
 
 async function secondaryWithDestinations(page: Page): Promise<{
   urn: string; destinations: any;
@@ -2431,17 +2440,28 @@ async function secondaryWithDestinations(page: Page): Promise<{
     .filter((s: { phase?: string; attainment_8_score?: number | null }) =>
       s.phase === 'Secondary' && s.attainment_8_score != null)
     .map((s: { urn: number }) => String(s.urn));
+  expect(urns.length).toBeGreaterThan(0);
 
+  let served = false;
   for (const urn of urns.slice(0, 25)) {
     const detail = await page.request.get(`/api/schools/${urn}`);
     if (!detail.ok()) continue;
     const data = await detail.json();
+    // The key must exist, even as null. Its absence means the backend in front
+    // of us does not know about destinations at all.
+    if ('destinations' in data) served = true;
     if (data.destinations?.ks4) return { urn, destinations: data.destinations };
   }
-  throw new Error(
-    'No secondary school returned a destinations block. Either the annual EES '
-    + 'DAG has not run on this environment, or the destinations marts are empty.',
-  );
+
+  expect(served,
+    'GET /api/schools/{urn} served no `destinations` key at all — the backend '
+    + 'is missing this feature, not merely missing its data').toBeTruthy();
+
+  test.skip(true,
+    'No school has destination data yet: the annual EES DAG has not run on '
+    + 'this environment. The API shape is correct, so this is a data-load '
+    + 'precondition rather than a regression.');
+  throw new Error('unreachable');
 }
 
 test('a secondary school page says where its Year 11 leavers went', async ({ page }) => {

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

@@ -22,7 +22,7 @@ const ALL_PUBLISHED = [
 
 const fullPhase: DestinationPhase = {
   cohort_year: '2022/23',
-  groups: { all: { cohort: 180, categories: ALL_PUBLISHED, aggregates: {} } },
+  groups: { all: { cohort: 180, categories: ALL_PUBLISHED } },
 };
 
 const suppressedPhase: DestinationPhase = {
@@ -36,7 +36,6 @@ const suppressedPhase: DestinationPhase = {
         cell('apprenticeship', 8), cell('employment', 6),
         cell('not_sustained', 5), cell('not_captured', 4),
       ],
-      aggregates: {},
     },
   },
 };

nextjs-app/__tests__/components/Post16DestinationsSection.test.tsx

@@ -14,7 +14,6 @@ const phase: DestinationPhase = {
         { category: 'employment', pupils: 13, percentage: 13.5, status: 'published' },
         { category: 'not_sustained', pupils: 6, percentage: 6.3, status: 'published' },
       ],
-      aggregates: {},
     },
   },
 };

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

@@ -1,5 +1,5 @@
 import {
-  canAggregate, aggregateCells, canRenderPublishedAggregate,
+  canAggregate, aggregateCells,
   canRenderBar, toBarSegments, CARD_GROUPS,
   type DestinationCell, type DestinationGroup, type DestinationCategory,
 } from '@/lib/destinations';
@@ -19,7 +19,6 @@ const fullGroup = (): DestinationGroup => ({
     pub('apprenticeship', 8, 180), pub('employment', 6, 180),
     pub('not_sustained', 5, 180), pub('not_captured', 4, 180),
   ],
-  aggregates: {},
 });
 
 describe('canAggregate — R2, computing from components', () => {
@@ -47,26 +46,6 @@ describe('aggregateCells', () => {
   });
 });
 
-describe('canRenderPublishedAggregate — R2, a total DfE published itself', () => {
-  it('allows it when no component is suppressed', () => {
-    expect(canRenderPublishedAggregate([
-      pub('school_sixth_form', 75, 180), pub('sixth_form_college', 21, 180),
-    ])).toBe(true);
-  });
-
-  it('REFUSES it when exactly one component is suppressed — the aggregate identifies it', () => {
-    expect(canRenderPublishedAggregate([
-      pub('school_sixth_form', 75, 180), sup('sixth_form_college'),
-    ])).toBe(false);
-  });
-
-  it('allows it when two or more components are suppressed', () => {
-    expect(canRenderPublishedAggregate([
-      sup('school_sixth_form'), sup('sixth_form_college'),
-    ])).toBe(true);
-  });
-});
-
 describe('canRenderBar — R1', () => {
   it('allows a bar when the whole group is published', () => {
     expect(canRenderBar(fullGroup())).toBe(true);

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

@@ -17,7 +17,6 @@ const phase = (categories = 1) => ({
         category: 'school_sixth_form' as const,
         pupils: 75, percentage: 41.7, status: 'published' as const,
       })),
-      aggregates: {},
     },
   },
 });

nextjs-app/components/school/DestinationsView.tsx

@@ -39,7 +39,6 @@ function toGroup(payload: DestinationGroupPayload): DestinationGroup {
   return {
     cohort: payload.cohort ?? 0,
     cells: payload.categories,
-    aggregates: payload.aggregates,
   };
 }
 

nextjs-app/lib/destinations.ts

@@ -5,9 +5,13 @@
  * DfE suppresses individual cells with `c`, and the destination categories sum
  * to the cohort. So subtracting the published cells from the cohort total
  * recovers a lone suppressed cell exactly — which is the case on 22% of
- * mainstream secondaries. The guards below are what stop this module's
- * consumers doing that by accident, and they are why a percentage is never
- * reconstructed from a partial sum.
+ * mainstream secondaries.
+ *
+ * The guards here are the SECOND line of defence, not the first. Not drawing a
+ * number does nothing to stop it being computed, so the real fix lives in
+ * backend/data_loader.py::_mask_for_disclosure, which withholds a companion
+ * cell before the figures ever leave the server. These functions keep the UI
+ * honest about what it draws from an already-safe payload.
  *
  * See docs/superpowers/specs/2026-08-28-destination-measures-design.md.
  */
@@ -40,8 +44,6 @@ export interface DestinationCell {
 export interface DestinationGroup {
   cohort: number;
   cells: DestinationCell[];
-  /** Aggregates DfE published itself, keyed by slug. */
-  aggregates: Partial<Record<'sustained_education' | 'sustained_all', DestinationCell>>;
 }
 
 /** Display order, which is also bar order: education, then work, then absence. */
@@ -80,15 +82,6 @@ export function aggregateCells(
   return { pupils, percentage: (pupils / cohort) * 100 };
 }
 
-/**
- * R2, the other direction: DfE published this total itself. Showing it beside
- * the components is safe only when it spans no suppressed component, or two or
- * more. Exactly one, and the total names the withheld figure.
- */
-export function canRenderPublishedAggregate(components: DestinationCell[]): boolean {
-  return suppressedCount(components) !== 1;
-}
-
 /** R1: a bar is drawable only when nothing in the group is withheld. */
 export function canRenderBar(group: DestinationGroup): boolean {
   return group.cohort > 0 && group.cells.every(c => c.status === 'published');

nextjs-app/lib/types.ts

@@ -616,8 +616,6 @@ import type { DestinationCell, PupilGroup } from './destinations';
 export interface DestinationGroupPayload {
   cohort: number | null;
   categories: DestinationCell[];
-  /** Totals DfE published itself. Never computed here — see lib/destinations.ts. */
-  aggregates: Partial<Record<'sustained_education' | 'sustained_all', DestinationCell>>;
 }
 
 export interface DestinationPhase {