In the past three weeks, I have received eight requests to admit new pupils - three refugees, an excludee, a child with serious behavioural difficulties (from a neighbouring borough), and three who simply want a transfer. We have reports for five of them: they indicate that the children are of limited ability, have poor motivation, are disruptive and attend irregularly. If I admit these pupils they will lower our exam and attendance statistics and, in some cases, adversely affect the behaviour of the classes in which they are placed. But the school is heavily oversubscribed in Year 7, and has few vacancies in other year groups.

Other schools are not so fortunate. They may have spare capacity and can be required to admit all-comers, often with disastrous consequences. It seems obvious that when disruptive children are concentrated in a few schools the learning ethos quickly deteriorates, and they become, in the new terminology, bog-standard. Even in these schools, there are many pupils who want to learn. There are also many who will work well in an environment where good standards of work and behaviour are the norm.

And then there are the disrupters themselves. That increasing minority who will not work or co-operate. The parents of many of these children have long since lost control. The political imperative of “social inclusion” is important because it is attempting to keep these, and many other young people, in full-time education. I guess that those who support the idea of social inclusion in theory would add in private, “Ias long as they aren’t in the same class as my kids”.

If all schools were required to admit a quota of difficult children (just as many are allowed to select on ability), the disruptive children wuld be spread around and would become more manageable. The reality is that schools with a large proportion of high-achieving pupils know that they could not cope. And parents would not tolerate it. For instance, in a school in which parents can be confidently asked to pay pound;30 a month to pay off school debts, can you imagine their response to the admission of a child who is violent, abusive and disruptive? The result is that there are too many state schools which are allowed to get away with saying that they are full when there are difficult children seeking admission, yet find vacancies when there are pleasant and well-motivated youngsters needing a place. And legislation, by default, permits it.

Legislation, on the other hand, makes it difficult for community (sorry, bog-standard comprehensive) schools to refuse to admit difficult children, and makes it hard to exclude them permanently. There have always been some children who gave up on school long before the legal leaving date. The questions that we have to ask are: why did this happen, why does it continue to happen, and how can we change the situation? If we do not ask the right questions, we are unlikely to get the right answers.

As long as political rhetoric relies on insults and half-baked answers to the wrong questions, we will not even begin to fulfil that duty. The real problems legislation has caused for many young people (and their teachers) will remain unresolved. Why is it that Downing Street’s contemptuous remark directed at those pupils and their teachers has an echo that sounds like “bog-off”?

Our government could learn some salutary lessons from their predecessors. It is only a few years since former education secretary John Patten branded parents who disagreed with him as “neanderthal“I and look what happened to him.

Dr Stuart Newton is head of Selsdon high school, Croydon, south London