In some British primary schools, each class is equipped with women who function as Behaviour Support Assistants. They take over the disruptive children and thus allow the tranquillity needed for a little actual teaching. A difficult child, reported Dispatches, might be asked to choose - choose! - whether he was prepared to go back into class and behave, otherwise he would be shepherded into a "quiet room" without distractions, in order to cool down. These children are ten or younger, and the pathos of their being asked to "make choices", when they have never acquired the integrated mentality needed for that sophisticated act, is piteous to behold.

Understanding some of the elements of this change requires bringing to the surface thoughts and feelings that have not yet found even a proper name, much less an intellectual focus. First, however, let me bring out the new situation by contrast. Think back before the watershed 1960s, and the contrast is instructive.

Then, children had defined places in a classroom and learned rapidly the decorum necessary for school life. There was no question of choosing whether or not to behave, because there was an order of conduct enforced by the teacher and it applied to everyone. The teacher was "an authority figure", and like all authority figures inspired a certain amount of fear, part of which depended on the possibility of physical punishment. Such punishment was seldom used, but it was part of an understood world. As a supply teacher in a variety of primary and secondary modern schools around Brixton, south London, for 18 months in those days, I only once had occasion to call for the cane, which was sent (with the caning record book) straight up from the headmaster's office. As I raised the cane over the offender's hand, a chorus came from the class: "Mustn't raise the cane above your shoulder, Sir, LCC regulation." These were children who had not yet been accorded the absurdity of rights, but they understood very well that they lived under a rule of law.

The insistent question is this: how is it that so many schools have moved from the orderly world of that time to the violent distraction and educational failure of today? It is a complicated story in which the causal links can only be speculative. We must, of course, recognise that we are a very different society from that of two generations ago, better no doubt in some ways, worse in others. And the causal links we detect are only ever part of the story.

Many social conditions have been identified as part of the change, but behind most of them, I suggest, is a massive change in our moral sentiments: notably, a rise in the currency of politicised compassion. This is a sentiment so much part of the air we breathe that it does not even have a name of its own. I began to be fully aware of it only in 2002, the year in which Teresa May, then chairman of the Conservative Party, electrified politics by suggesting at the party conference that many people regarded the Conservatives as "the Nasty Party". "Nice" and "nasty" began to surface out of the deeper waters of moral thought and sentiment to become actual tokens of political discussion, so we may for convenience call this whole tendency by the unlikely name of "the niceness movement". In these terms, the supreme moral virtue is compassion.