Knife-wielding pupils are returning to schools which have expelled them, because of the government's campaign to reduce exclusions, says a head teachers' union.

The National Association of Head Teachers claims that government targets on cutting exclusions mean that schools have to take back pupils who have attacked teachers.

David Hart wants head teachers to be able to expel violent pupils

The association, beginning its annual conference on Tuesday in Jersey, heard that the reluctance of local education authorities and their appeals panels to permanently exclude meant that disruptive pupils could cause havoc.

The association's general secretary, David Hart, said that in the past few weeks alone, two secondary schools in London had been forced to take back pupils who were wielding knives and threatening fellow pupils.

He could not name the schools because the heads were worried about the effect on their schools' reputations.

"In one case it wasn't just a knife it was a carving knife, wielded by an older student at a younger student," he said.

Head teacher Angeles Walford said she had been seconded for five months from her school in Wimbledon to try to turn round a failing school, also in the London area.

"The behaviour of the children was dreadful," she said.

She excluded a 12-year-old boy for two weeks for hitting a teacher but ran into considerable resistance from those who argued that he should be given another chance.

"We did give him another chance, and three weeks after he hit another teacher," she said. He was then permanently excluded.

Head teacher Angeles Walford had to take back pupils who had hit teachers

An NAHT executive member, Sue Sayles, said the problem applied to primary schools too - where often there were only female staff facing violent pupils.

"Our advice to members is to call the police," she said.

Head teachers say they must have the right to exclude pupils where their behaviour threatens the safety or education of others - even if it does not fit the government's guidelines or appeal panel decisions.

Long-running complaint

The row over the issue has been going on since the government issued a circular last year on how schools were to interpret the exclusion procedures set out in the School Standards and Framework Act.

Heads argued that it made it all but impossible for them to expel pupils because they must first go through "a range of alternative strategies" such as removing privileges, detention, mentoring and a support programme tailored to the individual pupils concerned.

The government guidance was revised in a letter sent out by the Department for Education in January.

This said there could be permanent exclusion for a first offence, for example involving violence, provided the head teacher did not use the sanction "in the heat of the moment".

But the union says this revised guidance does not seem to be registering with local education authorities.

Education authority appeals panels hear appeals from parents whose children are being kicked out of a school.

Their decisions are binding on all involved - so if they decide to reinstate pupils the school has no option but to take them back.

But Mr Hart said the problem was now so acute the union was exploring whether it might be possible to challenge such decisions in the High Court.

It might well soon have to advise its members to ignore appeal panel decisions - parents of other children would demand it.

A way of doing this might be to re-exclude a violent pupil so that the whole process began again.

Special units

Expulsions are falling. In 1998/99, 10,400 pupils were permanently excluded - 15% fewer than the 12,300 expelled in 1997/8.

During the 1990s there had been a huge increase - up from about 3,000 pupils a year at the beginning of the decade.

The Education Secretary, David Blunkett, recently announced another 420 learning support units, which provide special help for disruptive pupils - getting them out of mainstream classes but keeping them within schools until they can be re-integrated.

The government credits these with helping to bring about the drop in exclusions.

But teachers' unions have been critical, complaining that the children are nevertheless still in school and potentially causing trouble.

Mr Hart said some of his members did not agree with the idea - they felt the most disruptive pupils needed to be elsewhere altogether.