Pupils were the biggest culprits, threatening a quarter of the 501 teachers who took part in the poll. One in eight teachers reported they had received threats from a parent.

While only one teacher had been physically attacked by a parent, more than 40 per cent of teachers threatened by pupils had also been assaulted in the past 12 months.

Those most at risk of attack were teachers with less than five years’ experience; women; under 30-year-olds and teachers in special schools. Heads and deputies were also more likely to be assaulted than classroom teachers.

Two-thirds said that standards of pupil behaviour have declined since the last general election. Only one in 20 believes it has improved.

The poll sugests that Labour will lose votes for failing to stem the tide of disruption in schools. The party’s support among teachers who believe that pupil behaviour has worsened is four points lower than the 54 per cent of all teachers who say they would vote Labour. By contrast, 62 per cent of teachers who believe that pupil behaviour has not declined support Tony Blair.

Despite the mounting concern over discipline, teachers are overwhelmingly against a return to the rod. Only one in seven wants the cane to be used again in schools, compared to more than four in five who do not.

Instead they back their unions’ call for headteachers to decide whether or not pupils should be excluded from school. Perhaps surprisingly, deputies had the least confidence in heads. Only 76 per cent backed their boss to make the right decision compared to 84 per cent of all teachers.