Head teachers and the police are failing to offer staff the support they need to deal with the problem, says the Association of Teachers and Lecturers, which opened the classroom unions annual conference season yesterday in Torquay, Devon.
David Blunkett, Labour's education spokesman, will address the conference today, saying that schools should be given greater powers to exclude violent pupils, and that difficult children should be sent to special units for up to a term.
He said his card proposal was based on a system at a primary school in one of the most deprived areas of Newcastle. "It has improved behaviour significantly through the introduction of a system of yellow and red cards. These provide warnings and controls which are readily understood by the children."
The 150,000-strong association surveyed its branch secretaries in 71 local authorities. Half said that discipline was a worse problem than 15 years ago, and a further 35 per cent said it was much worse.
There were 293 assaults on teachers in the past year in 28 areas where detailed records were kept. Staff were worried about threats to their safety from pupils, parents and intruders.
Peter Smith, general secretary of the association, said many schools swept incidents under the carpet because of fears that they might be marked down as having discipline problems.
"We are talking about flick-knives being thrown at teachers, teachers being head-butted by irate parents. We are talking about intruders coming on to school premises and causing mayhem," he said.
Most of the branch secretaries surveyed blamed a deterioration in society for the indiscipline, while others cited poor adult role models, large classes and failures in the law.
One teacher who had had to take early retirement after an attack by a pupil, said in a statement yesterday that it seemed children could do no wrong. "Could the theorists explain just what ought to be done about a boy of eight who puts a stick in dog's mess and puts it in a younger boy's mouth?", he asked.
Another teacher, Galina O'Connor, 58, had to leave her job at a north London primary after receiving back injuries while trying to restrain a pupil.
The boy, nine, a refugee from Zaire, had previously kicked her and attacked fellow pupils, she said. But she had been advised by her deputy head to give in to demands from the boy for easier work, more praise, priority access to the computer and the right to sit wherever he wanted.
The boy was not excluded from Woodcroft primary, in Barnet, though he left soon afterwards to move to another borough. Mrs O'Connor received compensation of pounds 2,500.
"My life is absolutely ruined," she said yesterday.
A spokesman for Barnet council said it had never accepted that the boy had intentionally attacked Mrs O'Connor and that its compensation payment was without prejudice.
Mr Blunkett will criticise limits on school exclusions. At present, schools can exclude a child for up to 15 days or expel them. Gillian Shephard, Secretary of State for Education, is reviewing the limits.
In a separate survey it emerged yesterday that school buildings were falling apart. More than 600 primary schools still have outside toilets, and for more than 750,000 children the classroom is a temporary hut.