The standard catchment area pattern, as in the example above, has a well-defined central core surrounded by outlying dots. These outliers usually represent siblings - children whose parents have moved out of the catchment but who still get a place because they have a brother or sister at the school.

As school admission battles hot-up parents have been warned that if a child gains a place on the basis of false information, their child may be removed from the school. Poole in Dorset made headlines when it used anti-terrorist legislation to spy on three families suspected of catchment cheating.