Both detail views fetched /api/national-averages in a useEffect, so the
England-comparison deltas popped in after hydration and every section that
uses them was pinned to the client. The page now fetches it in parallel with
the school details (backend-cached 1h, degrades to null) and passes it down.
Removes one client round-trip per detail page and unblocks the section
extraction.
Characterization tests pass unmodified; only the render helper changed.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
