Code review found the disclosure the whole design was meant to prevent.
R1 was written as a rendering rule and implemented as one: canRenderBar
stopped the bar being drawn, but GET /api/schools/{urn} still carried the
cohort and every published category. cohort - sum(published) returned
Whitley Bay's withheld further-education figure exactly — 18 pupils — to
any caller, and the RSC payload put it in the browser too.
app.py already stated the principle for admission_distance: this endpoint
is public and unauthenticated, so a field left in the payload is a
published field. The same reasoning applies here and did not get applied.
_mask_for_disclosure now closes both identities before serialisation —
categories sum to the cohort, and disadvantaged + other = all — by adding
secondary suppression until every row and column hides none or at least
two. My first attempt picked the smallest published cell as the companion
and a new test caught it choosing a zero, which protects nothing: the
residual still resolved to 18. The companion must carry pupils.
DfE's own aggregates are no longer served. Nothing rendered them, and one
spanning a single suppressed component names it.
Cost, measured over 262 mainstream secondaries: the all-pupils bar
survives on 94% rather than 100%. Zero lone-suppressed groups remain.
The e2e helper now tells a missing feature apart from missing data: it
fails if the API serves no destinations key at all, and skips if the key
is served but the annual DAG has not populated the marts. Failing on the
second would redden the staging gate for unrelated commits.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BvdDKvFFSZuMVDH5fEyTob
The 'Post-16 destination data coming soon' note is deleted rather than
reworded: for a school with no sixth form the truthful statement is that
the question does not apply, and a placeholder there implies something is
missing. hasSixthForm and .sixthFormNote go with it — nothing else used them.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BvdDKvFFSZuMVDH5fEyTob