docs: design for similar schools nearby on the detail page
A school page links outward to its places and never to another school. This section adds that edge: three nearby schools of the same phase and a comparable intake, each a crawlable link and each addable to the basket. The design separates hard filters from soft preferences and never confuses them. Selectivity, provision and opposite-sex intake are claims the section cannot make, so they never relax, even where that means no section renders. Gender and religious character describe closeness of fit, so they relax in tiers — and the card states what actually survived rather than padding with a match it did not earn. Includes the mockup the design is drawn against, with all three tier states live in both themes. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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# Similar Schools Nearby — Design
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**Date:** 2026-09-21
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**Status:** awaiting review
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**Scope:** school detail pages, both phase templates
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## Goal
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Give a school detail page an answer to the question every reader arrives with
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after the results tables: *and what else is around here?*
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Today a school page links outward to its place pages through
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`components/school/NearbyPlaces.tsx` and nowhere else. It never links to another
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school. This section adds that edge — three nearby schools of the same phase and
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a comparable intake, each a crawlable link and each addable to the comparison
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basket in one click.
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Mockup, with all three tier states live in both themes:
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<https://claude.ai/artifact/168KdUMcfkUeGWW2FGjuec>
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Source of the same page in the repo: `mockups/similar-schools-nearby.html`.
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## The constraint that shapes everything
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**A nearby school is not automatically a comparable school.**
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The section's whole value is that a reader treats what it shows as a shortlist.
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That makes every card an implicit claim that the school is a realistic
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alternative, and there are three ways that claim goes wrong:
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1. A **selective** school beside a non-selective one. Their intakes are
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different by construction, so putting their Attainment 8 figures side by side
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invites a conclusion the data cannot support.
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2. A **special school, PRU or AP** beside a mainstream school. This is the same
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error PR #70 fixed for the England benchmark, where Greenmead (URN 101099)
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rendered "0% — 62 below England".
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3. A **single-sex** school of the opposite sex. Not a weak match — not an option
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at all.
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So the design separates two kinds of rule, and never confuses them:
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- **Hard filters** encode the claims above. They are never relaxed, at any
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distance, even if that means the section does not render.
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- **Soft preferences** describe how closely the intake resembles this school's.
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They relax in tiers, and the card's own text always states what survived.
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Everything below follows from that split.
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## Selection algorithm
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A backend helper, `_similar_schools_payload(urn)` in `backend/app.py`, modelled
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on the existing `_places_payload(urn)` and operating on the cached
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`load_latest_school_data()` frame — one row per URN, already carrying
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`latitude`, `longitude`, `phase`, `gender`, `religious_denomination`,
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`admissions_policy`, `school_type` and `status`.
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### Hard filters
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| Filter | Rule |
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|---|---|
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| Self | `urn` is excluded |
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| Status | GIAS status must be open |
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| Coordinates | both `latitude` and `longitude` present on both schools |
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| Phase | same phase group via the existing `PHASE_GROUPS` map |
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| Provision | special/PRU/AP match only each other |
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| Selectivity | selective matches selective; non-selective matches non-selective |
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| Gender | Boys never matches Girls; Mixed is compatible with both |
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`PHASE_GROUPS` is reused rather than re-derived so an all-through school is
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offered correctly on both the primary and secondary sides, exactly as it already
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behaves in search.
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The provision filter needs a backend counterpart to the frontend's
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`isSpecialSchool()` in `nextjs-app/lib/utils.ts:897`, reading the same GIAS
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establishment types through `backend/gias_codes.py`. The two must agree: a
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school the frontend treats as special for benchmarking but the backend treats as
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mainstream for matching would be dropped from its own England comparison and
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then offered as a peer to a mainstream school on the next page along.
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**Three cards.** The target count is 3, which is what the grid is built for; 2
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is the minimum that renders at all.
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### Soft preferences, relaxed in tiers
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| Tier | Additionally requires | Radius |
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|---|---|---|
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| 1 | exact gender equality **and** same religious character | 3 miles |
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| 2 | exact gender equality | 5 miles |
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| 3 | nothing beyond the hard filters | 10 miles |
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Candidates are taken from tier 1 first, ordered by distance; if fewer than three
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have been found the next tier tops up, and so on. A school already taken cannot
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be taken again by a later tier.
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**Faith relaxes before gender.** A faith mismatch changes the character of a
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school; a gender mismatch can mean the school is not available to the reader's
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child at all. Ordering them the other way would fill the section with schools
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that cannot be applied to.
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### Two decisions that are easy to get wrong later
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**Selected by tier, displayed by distance.** Tier decides *which* three schools
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earn a slot. The rendered order is then distance ascending, because "nearby" is
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the promise in the heading and a reader scanning the row reads the first card as
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the closest. A tier-2 school at 0.4 miles therefore appears above a tier-1
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school at 2.9 miles, and the chips explain the difference in match quality.
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**Fewer than two results renders nothing.** Not an empty state, not a single
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lonely card, not padding with schools that failed the hard filters. The section
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is absent, the nav item is absent, and the page is unchanged from today. A page
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with one weak match is better off without the section than with it.
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### Distance
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Straight-line, from the vectorised haversine already used for postcode search at
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`backend/app.py:831`, computed over the ~27k-row frame in numpy. Reported to one
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decimal place in miles, consistent with the rest of the site.
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Straight-line distance is not road distance and is not measured from the
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reader's home. The section says so in its disclosure rather than leaving the
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reader to assume otherwise.
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## API
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`/api/schools/{urn}` gains a `similar_schools` array. Each row:
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| Field | Notes |
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|---|---|
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| `urn` | for the link and the compare basket |
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| `school_name` | link text |
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| `distance_miles` | one decimal place |
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| `school_type` | GIAS type, translated, for the card's meta line |
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| `age_range` | for the meta line |
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| `shared` | the chip strings the tier actually justifies — see below |
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| `tier` | 1, 2 or 3 — drives the lede's wording and the chip styling |
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| `metric_value` | the phase-appropriate headline figure, or null |
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| `metric_key` | `rwm_expected_pct` or `attainment_8_score` — see below |
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| `metric_year` | the year the figure is from |
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The metric follows the template the page is rendering, not the neighbour's own
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phase, so a row of cards never mixes two scales. Primary and **all-through**
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pages use `rwm_expected_pct`, matching `PrimarySchoolSections`, which is the
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template all-through schools render with; secondary pages use
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`attainment_8_score`. Where the neighbour has no value for that key, the card
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reads "Not published" rather than falling back to the other key.
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`tier` is carried explicitly rather than inferred from the contents of
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`shared`, because the frontend needs it for two separate decisions — whether the
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lede may claim a similar intake, and whether a chip renders as a brand-tinted
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fill or a muted outline — and inferring it from chip count would couple those
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decisions to the copy.
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Three rows of roughly 130 bytes each. It rides in the existing detail payload
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rather than a new endpoint because the page already makes exactly one server
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fetch for its data, and `/school/[slug]` regenerates at most weekly
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(`revalidate = 604800`), so the per-request cost is paid once per school per
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week.
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**The key is absent, not null, on a backend that does not have this code.** The
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frontend treats absent and empty identically, which is what allowed
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`NearbyPlaces` to ship without a lockstep deploy of the two images.
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`shared` is computed on the backend beside the tier that produced it, not
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re-derived on the frontend. Deriving it twice is how a card comes to claim a
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match the selection did not actually make.
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## Frontend
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### Components
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`components/school/SimilarSchoolsSection.tsx` — a server component wrapped in
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the shared `Section` shell from `sectionShared.tsx`. It renders the heading,
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the lede, the `<details>` disclosure, the card grid and the footer CTA. Every
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card's title is an `<a>` to the school's canonical slug URL via `schoolUrl()`.
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`components/school/AddToCompareButton.tsx` — the only `'use client'` file this
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adds, and the only client JavaScript in the section. It calls `addSchool` from
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`ComparisonProvider` and reports the selection with a `from: 'similar_schools'`
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attribution, mirroring `addSchoolFromSearch` in `HomeView.tsx:442`.
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The split matters: the links — the part with SEO value and the part that must
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work without JavaScript — are server-rendered into the initial HTML, and only
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the basket interaction is hydrated.
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### Placement and navigation
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Rendered as the last section **inside** `SchoolDetailShell`, from both
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`PrimarySchoolSections` and `SecondarySchoolSections`. Inside, not after, because
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the sticky nav's scroll-spy locates sections with `document.getElementById` and
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can only reach a section that lives in the shell.
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`NearbyPlaces` stays where it is, outside the shell, immediately below. The
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resulting order — this school, then similar schools, then the places containing
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them — narrows before it widens, which is the order a reader leaves a page in.
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`buildNavItems` and `buildSecondaryNavItems` both gain
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`{ id: 'similar', label: 'Similar schools' }`, gated on the section rendering.
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The id must match the `Section` id or the scroll-spy silently breaks.
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### The comparison CTA
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A plain `<a href="/compare?urns=…">`, built from this school's URN plus the
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selected ones. `/compare` already parses `urns` from the query string
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(`app/(frontend)/compare/page.tsx:55`), so this needs no new compare plumbing.
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With nothing selected the CTA is disabled; the button also adds to the shared
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basket so the site-wide comparison state stays consistent with what the page
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shows.
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## Copy, and what the section is allowed to claim
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**The lede tracks the tier.** At tiers 1–2 it reads "Other primary schools near
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X, with a similar intake." At tier 3 it drops "with a similar intake", because
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at tier 3 that is not what was matched.
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**Chips state only what is shared.** A tier-2 card carries fewer chips rather
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than a chip it has not earned; a tier-3 card falls back to the plain phase name,
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styled as a muted outline rather than a brand-tinted fill so the difference is
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visible at a glance.
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**The neighbour's metric carries no valence colour.** Green and terracotta are
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reserved site-wide for comparison against the England average. Colouring a
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neighbour's figure against this school's would read as ranking the neighbours
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against each other, which is precisely the endorsement this section must not
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make. The figure sits in neutral ink above a plain "72% at this school"
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reference line, and the reader draws their own conclusion.
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**A missing figure reads "Not published".** Never 0, never blank, never an
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em dash. This follows the same rule the rest of the detail page uses: a school
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with no published result has not scored zero.
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**The disclosure states the method plainly** — same phase, nearest first,
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preferring a similar intake, special schools only ever compared with special
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schools, straight-line distance from the school rather than road distance or
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distance from the reader's home, and that being listed here is not a
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recommendation.
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## Degradation
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| Condition | Behaviour |
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|---|---|
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| `similar_schools` absent (older backend image) | no section, no nav item |
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| fewer than 2 qualifying schools | no section, no nav item |
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| this school has no coordinates | no section |
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| the helper raises | returns `[]`; the page renders without the section |
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The helper is wrapped so a failure inside it never 500s a page that is otherwise
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complete — the posture `get_supplementary_data` already takes for its own
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queries.
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## Testing
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**Backend**, in a new `backend/tests/test_similar_schools.py`, against a
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synthetic frame rather than live marts:
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- a selective school never returns a non-selective one, and vice versa
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- a special school returns only special schools; a mainstream school returns none
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- a Boys school never returns a Girls school; Mixed matches both
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- closed schools and schools without coordinates are never returned
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- tier relaxation fills in order, and a school taken at tier 1 is not repeated
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- an all-through school is offered on both phase sides
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- fewer than two qualifying schools returns `[]`
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- distances match a hand-computed haversine for a known pair
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**Frontend**, in `nextjs-app/__tests__`:
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- the section renders nothing for absent, empty and single-row inputs
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- the lede drops "with a similar intake" when any card is tier 3
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- a null metric renders "Not published"
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- the nav item appears only alongside the section
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**E2E**, added to the existing journeys in `e2e/tests` in the same PR, per the
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repository's rule on user-facing behaviour:
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- the section renders on a known staging URN, with resolving links
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- add-to-compare reaches `/compare` with the expected `urns`
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The E2E gate runs after merge on this project, so these journeys are not
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provable in the PR checks; the PR is verified on the unit tests, and the
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journeys are confirmed on the post-merge staging run.
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## Out of scope
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- A map of the nearby schools. The section is a list; the page already has a map.
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- Statistical neighbours on deprivation, size or cohort profile. If the tiers
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prove too coarse, that is the trigger to move this computation into a dbt mart
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— `_similar_schools_payload` is a deliberate seam for exactly that swap.
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- Precomputing neighbours in `marts.*`. Rejected for now: a new mart is inert
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until Airflow runs, so the feature would ship dark, and every tuning change to
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the tiers would become a pipeline round-trip instead of a deploy.
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- Any change to `/api/compare`, the compare page, or the comparison basket.
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