The crackdown on violent behaviour announced by Charles Clarke, the Education Secretary, this week comes amid growing concern about violence in schools.

The death of 14-year-old Luke Walmsley, stabbed in a school corridor last year, led to a national debate about children’s safety and how best to deal with violent pupils.

Luke was knifed in the heart by fellow pupil Alan Pennell, then 15, following a confrontation at Birkbeck secondary school in North Somercotes, Lincolnshire, last November. Pennell is serving life sentence for murder.

Luke’s case was a tragic illustration of the problems schools face in dealing with armed pupils.

Stephen Twigg, education junior minister, told Parliament last month that an estimated 1 per cent of pupils - 73,000 - had carried an knife in school for offensive reasons last year.

Twice the number carried a knife for self-defence, he said.

This week, an 11-year-old pupil from Fitzharrys School, Abingdon, Oxfordshire, was taken to hospital after being stabbed in the thigh on a school bus. Two boys were arrested and bailed.

According to the National Association of Schoolmasters Union of Women Teachers, two teachers were shot by children bringing ball-bearing guns into the classroom last year.

The union has campaigned for airport-style security checks at schools.

Chris Keates, NASUWT general secretary, said: “Schools remain relatively safe havens, but there is a growing weapon-carrying culture among young people and school security needs to be tightened in response.

“We are not saying every child should go through security checks before they enter a school but there should be a system of random checks with hand-held metal detectors to act as a deterrent.”

Unions will welcome the Government’s commitment to tackle the problem but many headteachers will be wary of using new powers to search pupils without calling in the police.

They want more protection for members who have to confront armed teenagers.

David Hart, National Association of Head Teachers general secretary, said disarming young people was “an issue for the police” and that teachers and support staff should not be asked to confront armed pupils without proper back-up.

John Dunford, general secretary of the Secondary Heads Association, said:

“Schools are becoming increasingly concerned about knives and weapon carrying generally. Teachers need confidence to search students using metal detectors and other means without being sued by parents under human rights or child protection legislation.”

Unions will also welcome measures to speed up cases involving allegations of abuse against teachers, but the Government’s refusal to allow anonymity for the accused is a disappointment.

Wrongly-accused teachers have faced public abuse, marriage breakdowns and even prison before clearing their name.

Marjorie Evans, head of St Mary’s primary, Gwent, became a cause cel bre in 2000 after being accused of assaulting a pupil. She spent 18 months clearing her name and later returned to school.

Mike Lawson, a former history teacher on Merseyside was sentenced to seven years after being found guilty of assaulting a former pupil. He spent almost three years in jail before having his conviction quashed on appeal.

Last year, an all-party parliamentary group looking into abuse allegations warned teachers not to teach “vulnerable” children alone because of the risk of malicious allegations.

The third plank of the Government’s proposals, limiting the number of excluded pupils that individual schools have to accept will receive a warmer welcome.

Critics have long complained that some schools have to deal with more than their fair share of problem pupils.

Those “sink” schools will hope that reducing the number of difficult pupils will lead to dramatic improvements in discipline. But neighbours who currently avoid excluded children may have to work a little bit harder.