Size determined by performance

17th November 1995 at 00:00
So the Office for Standards in Education has discovered that class size does not have much relationship to performance, particularly exam results. It is a finding which fits in nicely with the Government's view that increases in class size are unimportant.

OFSTED could have said more. There is actually a positive association between class size and exam results - the bigger the class, the better the results: even better from the Government's point of view. But this is not evidence that the former causes the latter.

The reason is obvious to people who work in schools - pupils who are slow learners are usually put into smaller classes while high-fliers are often in quite large classes.

The class size is determined by the performance, not vice versa.

Statisticians are aware that association is not the same as causation: the Government and OFSTED need to realise it too.

If you invert cause and effect, it is not surprising that you get nonsense.

JOHN BAUSOR Education consultant 5 Longcrofte Road Edgware, Middlesex

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