Many of the union delegates who heard the Education Secretary David Blunkett's proposals for more school "sin bins" felt they did not go far enough.

Teachers at the annual conference of the National Association of Schoolmasters Union of Women Teachers (NASUWT) in Llandudno gave him a warm reception.

They were pleased that he accepted more needed to be done to improve standards of behaviour in schools, and to remove disruptive pupils from the classroom.

But their leader, general secretary Nigel de Gruchy, has called for off-site "sin bins" to be set up in every town so that disruptive children can be taken out of mainstream schools altogether.

Speaking to journalists before Mr Blunkett's announcement, he said the secretary of state should "get real on how difficult these youngsters are to work with".

Parents' right of appeal

He had already urged the government to change the law so that off-site units could legally become part of schools, he said.

That would mean pupils could be referred there without being formally excluded - leaving parents with no right of appeal over the procedure.

The move would thus help the government achieve its targets for reducing exclusions but would help to protect teachers and pupils and stop children's education from being disrupted by a few unruly classmates.

Responding to Mr Blunkett's speech on Thursday he said the union did welcome learning support units, "even those in school".

But he told him: "We seriously question whether you've got the balance right between on-site and off-site units.

Andrew Lawson: "Other pupils are affected"

"There comes a time when the only one solution is the complete removal from the school premises."

Andrew Lawson, who teaches music in a Leicestershire secondary school, said that everything Mr Blunkett had said had come across as being "well-rooted in common sense".

But he said that perhaps the measures were "not going far enough", adding: "I do feel very strongly that there should be a physical separation for pupils showing certain levels of disruptiveness.

'Common sense'

"If the pupils are kept on site, they can still affect the other pupils, as they are together travelling to school, in the playground and in the corridors."

Polly Deb remains to be convinced

Polly Deb, a teacher at Westminster Primary School in Birmingham, said: "Although what Mr Blunkett said made good sense, it's all talk and no action yet.

"Everything he said was good, but we need to wait and see what comes of his promises.

"It all depends on how disruptive children are. I think the government needs to issue guidelines to schools to help them define degrees of disruptiveness, indicating whether pupils should be sent to on-site or off-site units."

Ms Deb said Mr Blunkett had made a good point about parents' duty to help encourage politeness and decency in the next generation, attempting to stamp out foul language and bad behaviour.

Peter Watts: "I don't believe him"

"How much can we do as teachers?" she said.

"I have my pupils between 9am and 3pm, and during that time I can make sure they behave well and stop them from using bad language. But that's as far as we can go."

Religious education teacher Russell Thomas, president of the union's Swansea association, said he agreed that money should be spent on on-site units, as they gave pupils the chance to reform and be reintegrated into mainstream schooling.

"Those who are extremely disruptive have got to go off site, those who assault pupils or staff, or who are persistently aggressive. But I've worked with difficult pupils over the years, and some pupils change.

Russell Thomas: "Pupils can change"

"If they were all sent to "sin bins" away from schools, those who reformed would probably have not done so."

Earlier at the conference, delegates unanimously backed a motion calling for an expansion of specialist support for disruptive pupils.

Some members told of their own knowledge of disruptive pupils, including those aged three and four who physically assaulted teachers, and children aged five and six who displayed "inappropriate sexual behaviour".

Steve Triffitt, a science teacher from Scarborough who seconded the motion, told how the inclusion of two unruly boys in one of his classes had forced him to plan two lessons for every teaching session with the class - one practical, and one theory.

Steve Triffitt: Double the work

He could only teach the practical lesson when the boys did not show up, as he could not trust them.

"Exclusion must happen, and parents must know that it is going to happen," he said.

Jules Donaldson, of the Sandwell association, said: "It is important that we ram home the increasingly problem of behaviour which is blighting the lives of colleagues up and down the country.

"It's not only workload - it's abuse on a daily basis which is driving some very good teachers out of the profession."

Peter Tippetts, of the Southampton association, said: "Children with specialist social needs and psychiatric needs need to be dealt with by specialists in these fields."