How do school admissions and catchment areas actually work?
Places are allocated by published oversubscription criteria, applied in order, when a school receives more applications than places — and "catchment" is only one of several possible criteria, not a guarantee of anything.
The process. You apply through your local authority on a single form, listing schools in genuine preference order, by the national closing date. Applications are matched centrally, and offers are made on a common offer day.
The equal preference system, which people misunderstand constantly. Every school considers every application without knowing what preference it was. Schools cannot favour applicants who put them first, and you cannot harm your chances by listing a popular school first. The old tactical behaviour of not naming a preferred school is obsolete and actively counterproductive.
Where more than one school would offer a place, you receive the one you ranked highest.
Typical oversubscription criteria, applied in the published order:
Children in care and previously in care, which is always first by law.
Medical or social need, with evidence.
Siblings already at the school.
Distance from home to school, measured by a stated method.
Catchment area, where the school uses one.
Faith criteria, for schools with a religious character.
Feeder schools, for some secondaries.
What "catchment" actually means. A defined area giving priority — not a guarantee, and not used by all schools. Many schools use straight-line distance with no catchment at all, in which case the effective admission distance varies every year with the number and location of applicants. Last year's cut-off distance is a guide, not a rule.
Address rules are enforced. Using a temporary or relative's address is fraud, and places are routinely withdrawn when discovered, including after a child has started.
If you do not get a place: accept the offer made — it does not affect anything else — join waiting lists, which are ranked by the same criteria and not by application date, and appeal to an independent panel.
Infant class size appeals face a much stricter statutory test.