One in three school principals were physically attacked last year and almost half were threatened with violence, prompting the lead researcher in a national study to warn that violence in schools is "out of control".

Principals reported being threatened with knives and guns, having furniture thrown at them, and being punched, headbutted and spat on. "I had a parent nod at a shotgun on their dashboard as they drove past me slowly and looked at me," said one.

They were just as likely to be threatened by parents as students, and those threats have been increasing with frequency during the eight-year duration of the Australian Principal Occupational Health, Safety and Wellbeing Survey.

They also face tougher job and emotional demands than the general population, and have higher rates of stress, burnout and difficulty sleeping. A quarter of them work more than 61 hours a week. Yet, despite all this, they also report higher job satisfaction.

The authors of the study surveyed 2365 Australian principals from all sectors last year. Violence was the most worrying finding, they said, with "concerning" upward trends in NSW and Victoria.