But the death of Philip Lawrence, the respected head at St George's Roman Catholic comprehensive in Maida Vale, London, was particularly shocking because it underlined a new and important phenomenon. Where once school- boys might have threatened sticks and stones, now they carry knives - and many are prepared to use them.
The new gangs in many London schools are split along ethnic lines: South Asian kids model themselves on the Hong Kong triads; Afro-Caribbean teenagers call themselves Yardies after the Jamaican drug rings. And the grown-up versions they emulate are reflected in the rising level of violence among children of every race. With a sideways glance at the US, we can only be grateful that British children do not have access to guns.
While the law has paid close attention to firearms, it has not caught up with the use of knives as vicious weapons. While crimes involving knives have gone up, children caught carrying open blades are usually just sent home with a caution. The police cannot arrest a young man for possessing a knife unless they suspect he will use it. It seems incredible that knives are not treated as harshly as other offensive weapons.
This may be because for too long we have seen knives as part of the Baden- Powell culture - tools for survival, rather than murder. Every trusty scout bears his sheath knife on his belt, ever ready to cut a rope, sharpen a tent peg or skin a rabbit. A law that developed around the romance of the past is failing to deal with the stabbing urban culture of the Nineties.
Tightening up the law on knives will be a start. But it will not solve all the problems of gang violence on city streets. Many adolescents who join street gangs have little to look forward to. There is a growing problem in our increasingly high-skilled economy about what to do with young men who have no qualifications. And the chances are particularly bad for young black men - in London, 60 per cent of them are out of work.
Thugs with knives must be stopped and punished. Mr Lawrence made it his mission at St George's to maintain discipline and stamp out violence. Before he died he told a local reporter: "When I first came here there was a group of youngsters who were intent on running the school themselves. I confronted them ... they expected me to walk away but I didn't. We do not tolerate consistent antisocial behaviour." We owe it to his memory to minimise the chances of such an incident ever happening again.Reuse content