Daily Telegraph Opinion 20 May 2006

We are asking the wrong questions. The raw horror of a knife attack on a 15-year-old strikes at our sense of what schools ought to be, and what teenagers ought to do. We naturally want to know how such a thing could happen. What has driven young people to this level of violence? Where do they get the idea? Is it from films, from "gangsta" music, from adults?

Yet these questions are based on a false idea, namely that aggression is learned behaviour. This notion has dominated universities and social services departments for 40 years, but has little foundation in fact. Any parent will tell you that young boys are naturally belligerent.

The only reason that infants do not do more damage is that their chubby fists lack strength. In most cases, by the time they are old enough to improvise weapons, their testosterone level is dropping, and they have started to calm down.

The relevant question is not "Where do they learn to be violent?" but "Where do they learn not to be violent?" Evolutionary biologists will tell you that there are natural reasons why all humans, especially males, are born with a capacity for thuggery (Christians have an equally coherent explanation: original sin).

Schools once took youthful aggression for granted, and sought to divert it into team sports. But modern educational theory, as usual flying in the face of observable fact, holds that violence is cultural. Where headmasters would once have put a brutish boy in boxing gloves and tried to channel his energies - or else simply threatened him with the use of greater violence - the modern head is as likely to encourage troublemakers to talk about what makes them angry.

Some children are naturally malicious, and schools should be ready to punish them to the extent that curtailing their malice becomes the rational choice.

At the same time, teachers should provide a properly disciplined framework so that acts of random brutality become harder to conceive. In a school where pupils have to cut their hair neatly, turn up on time and sit quietly in class, more serious offences will also be rarer. It is the educational equivalent of the "broken windows" theory of policing: just as an estate covered with graffiti advertises its lawlessness, so a youth accustomed to getting his way in small matters becomes likelier to transgress in big ones.

Above all, we should remember that all adults are, to some extent, authority figures. It takes courage, nowadays, to ask a loitering youngster why he isn't in school; but it is the right thing to do. If young people saw all adults as exercising a policing function, the paucity of real policemen might matter less.