And they also want tougher action from police to combat the increasing incidence of violence in schools.
Members of the Association of Teachers and Lecturers say far too often assaults go unreported as schools try to protect their reputations.
Yesterday ATL members meeting in Bournemouth backed calls for a change in the law so teachers can "defend themselves when attacked without fear of losing their jobs".
Rules which come into force in September will allow teachers to use "reasonable force" to restrain pupils. But the ATL is calling for teachers to have powers of restraint similar to the police or mental hospital staff.
Union guidance to teachers recommends that staff push away violent pupils or parents only as a last resort.
Brian Waggett, a teacher at Range High School on Merseyside, told the conference he was faced with calls for his sacking after defending himself when he was punched in the mouth by an angry pupil. The former oil rig worker said: "I defended myself. The parents of the pupil wanted me sacked. Thanks to ATL my job was saved.
"Your only defence is putting your face in the way. We are society's punch bags. Teachers should be able to defend themselves without fear of losing their jobs."
Terry Gallagher, a teacher at Top Valley School, Nottinghamshire, said he had been thrown to the ground and strangled by a pupil while supervising a tuck shop. He said: "It took three colleagues to remove his hands from my throat."
David Britton, of Skinners' Company's School for Girls in London, said one teacher had to be smuggled out of the school when a parent came to challenge her for confiscating a pupil's earrings. "Two years after Dunblane, intruders can still get into our school."
ATL general secretary Peter Smith said: "I do not think teachers are asking for a professional licence to clump anybody. What people are saying is that the pendulum has swung too far. Teachers using reasonable force to defend themselves risk being prosecuted."Reuse content