By Sean Coughlan
BBC News, at the ATL conference
Teachers are warning that pupils' violent behaviour is causing staff to leave the profession.
The ATL said bad behaviour was rampant
A third of teachers in the UK have faced physical aggression from pupils, a survey for the Association of Teachers and Lecturers (ATL) suggests.
And more than half have known of colleagues who had left teaching because of poor pupil behaviour.
This week, increased powers to enable teachers to restrain disruptive pupils came into force in England.
The ATL teachers' union, which is meeting for its annual conference in Bournemouth, is warning of "rampant" bad behaviour in classrooms.
Teachers blamed a "lack of parental guidance" for this widespread lack of respect for school staff.
And the union warned that the "inclusion" of such disruptive pupils in mainstream classes could damage the chances of other pupils.
The ATL said it surveyed primary, secondary and further education teachers in England, Wales, Northern Ireland and Scotland between 20 February and 9 March.
It found that many staff had to face intimidation, threats and physical attacks from pupils.
Verbal insults and threats had been experienced by 61% of teachers and 34% had been subjected to "physical aggression".
The survey found that 10% of teachers had suffered "physical harm" as a result of such attacks and 35% had suffered from "mental health problems".
Such behaviour problems had caused 56% of teachers to consider leaving the profession - and 54% reported knowing a colleague who had left teaching because of pupil indiscipline.
And teachers complained that they did not always receive adequate support.
The union cited the experience of an unnamed primary school teacher in Wiltshire who said: "A pupil hit me and I reported it to the head teacher but she made me feel I was in the wrong."
This week, teachers have been given extra powers to restrain violent pupils, with new laws coming into effect.
They explicitly state that teachers have the right to physically restrain and remove unruly pupils and impose detention.
A spokesman for England's Department for Education and Skills said the new powers gave heads and teachers "clear, statutory powers enabling them to deal with poor behaviour swiftly and decisively".
"Heads have never had such a range of disciplinary and preventative measures at their disposal, along with clear guidance on how to use them.
"They will now be able to send out a strong message to trouble-makers that if they misbehave, they can expect to be punished."
He added that strong discipline was crucial, but could only work along side responsible parenting and effective teaching on moral issues.
Another survey published on Tuesday by the ATL found that top-up fees could deter students from entering teaching.
And it warned that the cost of training could make teaching an increasingly middle class profession.