Estate agents sell "in catchment" as if it were a property attribute, like a garage. In most of England it is nothing of the sort. The phrase describes the output of an annual sorting process, and the output moves.
Start with who decides. Every state school has an admission authority. For community schools it is the local council; for academies, free schools and most faith schools it is the trust or governing body itself. Each authority publishes its own oversubscription criteria, within the rules of the statutory School Admissions Code, and those criteria only bite when applications exceed the published admission number, the PAN — the fixed count of places, say 30 for a primary form of entry or 210 for a secondary year group.
The criteria run in strict order. Children in local authority care, and those previously in care, must come first by law. After that, most schools prioritise siblings of pupils already on roll, then sometimes children of staff, faith commitments verified by a priest's or imam's reference, or attendance at a named feeder primary. Only when those groups are exhausted does distance decide who fills the remaining places. Distance itself is measured in ways that differ between authorities: some use a straight line from the home address point to a designated point on the school site, others the shortest safe walking route along mapped paths — and the two methods can rank the same two houses in opposite order.
This ordering is why the "catchment" most parents actually care about — the furthest home address that got a place — is recalculated from scratch each year. A large birth cohort, a bulge of siblings from earlier intakes, or one new block of flats near the gates can pull the last-distance-offered in by several hundred metres. Councils publish these figures annually, and the volatility is visible in the data: a school whose cut-off was 900 metres one September can close at 450 the next. Some authorities do draw formal catchment maps and give in-area applicants priority, but even there the map only reorders the queue; it does not create places, and in-catchment refusals are routine at popular schools.
Where the house-price gamble comes in
Researchers have repeatedly measured a premium on homes near high-performing schools — Department for Education analysis has put it at several per cent for primaries and more for the most sought-after secondaries, which in expensive areas translates to tens of thousands of pounds. The buyer is not purchasing a place, though. They are purchasing a probability, priced on last year's cut-off distance, which is precisely the number that is not guaranteed to repeat. A family that pays the premium and then loses out to a heavy sibling year has spent the money on a lottery ticket that came up short — and Brighton & Hove made the lottery literal in 2007, when it introduced random allocation as a tie-breaker within its catchment zones.
The application machinery adds its own wrinkles. Parents apply through their home council by the January deadline for primaries or 31 October for secondaries, listing up to six preferences in London and at least three elsewhere. The system runs on equal preference: schools never see where they ranked on your form, so listing a long-shot first costs nothing, and the council simply offers the highest-ranked school that can take the child. Offers land on national offer days — 1 March for secondary, 16 April for primary — and refused families can appeal, though infant class-size law caps reception, year 1 and year 2 classes at 30, which makes most primary appeals nearly unwinnable on the merits.
Because addresses carry so much weight, authorities police them. Application teams cross-reference council tax records, tenancy agreements and child benefit correspondence; short-term rentals taken solely for admissions season, or a grandparent's address used while the family lives elsewhere, are treated as fraudulent applications. The Code lets an authority withdraw an offer obtained by a misleading address even after the child has been allocated, and councils in London and the home counties report clawing back dozens of places a year this way.
The practical reading for parents is unglamorous: check the last three years of cut-off distances, not one; read the specific school's criteria rather than assuming distance rules; and treat any purchase premised on a single year's boundary as the bet it actually is.