Catchment maps: how they really work — and when not to trust one
Official boundaries, statistical estimates and radius circles can disagree by whole streets. How online catchment maps are actually made, and the verified cut-off data that decides real places.
Key facts
- There are three fundamentally different kinds of "catchment map" online: official council-published boundaries, statistical estimates modelled from past allocations, and simple radius circles — and they can disagree by whole streets.
- Most English councils publish no downloadable catchment boundary at all: School Atlas holds official polygons from 62 publishing sources, alongside links to 24,000+ schools' own council checkers.
- For oversubscribed distance-based schools, the decisive number is the last distance offered — the home-to-school distance of the final offer. School Atlas holds 21,800+ verified cut-off records covering 7,880 schools.
- An estimated heatmap can suggest an address is "in catchment" when the actual cut-off in the most recent round fell hundreds of metres short of it — and vice versa.
- The safest research pattern: official boundary (where one exists) + the council's own checker + the verified cut-off trend. Never rely on a modelled map alone.
Type “school catchment checker” into a search engine and you will find several tools happy to draw a confident line around your address. What those tools rarely explain is where the line comes from — and the answer varies so much that two popular websites can give a family opposite answers about the same house and the same school. This guide explains the three methodologies behind online catchment maps, what each one can and cannot tell you, and how to research an address the way an admissions officer would.
The three kinds of catchment map
What is actually behind an online catchment map
| Official council boundary | Published by the council or school as the formal priority area in the admission arrangements | The definitive answer to "am I inside the priority area?" | Being inside is priority, not a guarantee — oversubscribed schools still refuse in-area children |
| Statistical estimate / heatmap | Modelled from where past offers appear to have gone | A rough sense of a school's typical reach | It is an inference, not a rule — it can shade streets "in" that missed out in the real round, and it goes stale as demand shifts |
| Radius circle | A fixed distance drawn around the school gate | Almost nothing — admissions do not work in circles | Straight-line vs walking-route rules, priority bands and annual demand all ignored |
- Official council boundary
- Published by the council or school as the formal priority area in the admission arrangements
- Statistical estimate / heatmap
- Modelled from where past offers appear to have gone
- Radius circle
- A fixed distance drawn around the school gate
- Official council boundary
- The definitive answer to "am I inside the priority area?"
- Statistical estimate / heatmap
- A rough sense of a school's typical reach
- Radius circle
- Almost nothing — admissions do not work in circles
- Official council boundary
- Being inside is priority, not a guarantee — oversubscribed schools still refuse in-area children
- Statistical estimate / heatmap
- It is an inference, not a rule — it can shade streets "in" that missed out in the real round, and it goes stale as demand shifts
- Radius circle
- Straight-line vs walking-route rules, priority bands and annual demand all ignored
Many councils publish no boundary at all because their schools admit on distance rank, not a defined area — for those schools there is no true "catchment line" to draw.
Why the last distance offered beats any map
For a distance-tiebreak school, the only number that decided real places is the last distance offered: how far from the school the final successful applicant lived. It moves every year with sibling counts and local demand, which is exactly why it is more honest than a static line. School Atlas publishes 21,800+ verified cut-off records across 7,880 schools — including 16,400+ Reception cut-offs and 3,400+ schools with figures for the September 2026 round — each one traceable to a council allocation publication or FOI response, never modelled or interpolated. Where a school's cut-off has moved over several years, the trend tells you whether your distance is comfortable, marginal or unrealistic.
What we publish — and what we refuse to
School Atlas shows a catchment boundary only when a council has published one — we hold official polygons from 62 distinct official publishing sources, each displayed with its source and date. Where a council operates a postcode checker instead of publishing a map, we link the checker on the school's profile — for more than 24,000 schools — rather than inventing a line the council never drew. We do not display estimated boundaries, because a wrong “you're in” is more damaging than an honest “the council publishes no map — here is the real cut-off data instead”.
How to research an address properly
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