The knife incident at Whitefield School again brings to the fore the danger of young people carrying blades and will invariably lead to calls for US-style knife detectors at school gates.

Detectors, however, should be resisted. Incidents such as this, and the fatal stabbing of Kiyan Prince at London Academy in May, are still relatively rare. Engaging with youngsters about the dangers of carrying a knife is the best deterrent. This time, at Whitefield, the victim's injuries were not life threatening. But knives are such that even if the perpetrator does not intentionally mean serious harm, a slip of the hand during a frantic scuffle can easily be the difference between minor injury and death.