Teachers, then, have not been making it up: their job has been getting steadily harder. Research of such eminent respectability - co-edited by Professor Sir Michael Rutter, doyen of child psychiatrists and pioneer of research into school effectiveness, along with the criminologist Professor David J Smith of Edinburgh University - makes it harder than ever to dismiss the sort of concern expressed this week by the National Association of Head Teachers. An increasing number of children are now beyond control, the delegates at its Harrogate conference were told. In some cases schools are undermined by a lack of support from the wider community, parents in particular. And without support, said general secretary David Hart, a school’s task is impossible.

While such sentiments are often discounted as the predictable moans of an older generation about the state of youth, the teaching unions can point to a sizeable accumulation of evidence to the contrary. For example, the number of children permanently excluded has, risen dramatically: figures from the Office for Standards in Education suggest that 8,000 pupils were expelled in 199293. And this is taken to err on the side of caution. Permanent exclusions of pupils from primary school, at one time almost unheard of, are now a regular occurrence. The number of children requiring psychiatric help rose by a quarter in the second half of the 1980s and the number of those under the age of 10 doubled.

The underlying causes identified by Professors Rutter and Smith for such trends remain frustratingly unclear. Among their suspects for further interrogation are high levels of family discord, increasingly individualist ways of thinking and the heightened but unfulfilled aspirations associated with affluence. But their most definite conclusion is that there are no easy answers: television, for example, is not the principal culprit by itself, nor is poverty .

It is to be hoped that their book will also help discredit another very easy and incessantly repeated answer - that schools are the villains of the piece. Blessed with near-miraculous powers of moral and economic regeneration, teachers, it is alleged, have charted a course of anything-goes laxity.

Such criticism is absurd. School is, in reality, one of the few places for children where behaviour is strictly regulated and where the dominant ethos is of self-restraint and of respect for others and for the community. Faced with the sort of difficulty outlined in Professor Rutter’s research, and described daily by teachers and the psychological staff supporting them, this is by itself an impressive achievement.