Violent parents pose greatest threat to staff
David Hart, the NAHT's general secretary, promised full backing for heads forced to take the drastic step.
"People will argue this is visiting the sins of the parents on the pupils but when an assault has been committed the relationship between the parent and school might have been reduced to zero and the child would have a better chance of a fresh start in another institution," he said.
He spoke out as the NAHT revealed that 27 of its members had been assaulted in the past 12 months, and that heads were now almost twice as likely to be attacked by a parent as a pupil - 16 by parents, nine by pupils and two by the public.
Five heads have been awarded criminal injuries compensation of more than Pounds 5,000, including Pounds 12,000 for a head injury suffered when attempting to catch a burglar.
Another headteacher was awarded Pounds 7,555 for a back injury caused by a seven-year-old pupil, while Pounds 5,267 was awarded to a head kicked in the left leg by an eight-year-old.
Four weeks ago Liz Paver, NAHT vice-president, was dragged along the road by a car driven by a mother whose girl had been injured in a playground accident. Mrs Paver, head of Intake First School, Doncaster, lost a front tooth and suffered severe grazing to her arms and legs.
The mother has since apologised and the girl is still at the school. Mrs Paver said: "People are losing control more than in the past."
She said children now operated two codes of conduct - polite, well behaved, knowing the difference between right and wrong in school hours and something completely different outside it.
Moves to exclude the children of disruptive parents would place schools in confrontation with the independent appeals panels.
Conference called on local authorities to enforce codes of conduct after Nigel Holt from Stanton Middle in Milton Keynes told how he had been assaulted three times - once by a mother who set her dogs on him and another time when he had been given police protection after complaining about a father who had burnt his son with a cigarette.