The Secretary of State does not like “selection”. Nevertheless, where grammar schools exist, they may test children to see if they are “suitable for grammar school education”. If sufficient children of the necessary ability are not available, they may leave places empty. What are the implications of this? If the test is some form of “intelligence test”, what score equals “suitability for grammar school education” and how is that determined? Where rolls are falling, a grammar school that tries to keep its numbers up by lowering the pass rate might be thought to be acting outside its powers.

A small number of schools are still permitted to operate “partial selection” on ability to ensure a balanced intake. Most of these arrangements have been removed by the Schools Adjudicator. But, confusingly, it is still permissible to band.

A visiting Martian might be further confused by schools that are legally allowed to select by specialism. He might think a “performing arts” specialist school would be full of potential performers, but the rules ensure that specialism is more of a flavouring than a different product.

Schools specialising in sport, performing or visual arts or modern languages may only select 10 per cent of their intake for aptitude or “being able to benefit” from the specialism. Aptitude can be tested, but it is not at all clear how “being able to benefit” can, or how one might judge the relative merits of “those able to benefit” against those with talent.

There seems to be an ongoing pull between the desire for all schools to be the same so no child has to go to one that is different, and for variety to accommodate young people with different talents, aptitudes and interests. The law and the related codes reflect this tension and, dare one say it, confusion.

Richard Bird, Legal consultant to the Association of School and College Leaders.