The union has handled more than 200 cases in the past year and suggests these may only be the tip of the problem. It is urging councils to step up their procedures for tackling bullying at work. Only eight have specific policies.
Ronnie Smith, the union's general secretary, said: "There is evidence that temporary teachers, a rising proportion of the workforce, are even more worried about reporting such incidents because they fear that employers will terminate their contract without explanation and fail to re-employ them as new work becomes available."
The union says "a tiny minority" of senior staff make life a misery for subordinates or selected individuals.
"It has been undeclared war for seven years," according to one special school teacher prepared to break his silence, albeit anonymously. Mr A has been at loggerheads with his head and depute and repeatedly failed to gain promotion, largely, he believes, because of his negative school report.
"It seems only sycophants get on. The headteacher is in total control. I want to develop my career and it is being blocked. The headteacher's report has to be taken with a pinch of salt and it is an inappropriate way of assessing an individual," he says.
Mr A believes he is a good teacher and has taken further postgraduate qualifications. A recent HMI report on the school did not indicate any difficulties with his teaching.
Personal abuse has been a feature of the "domineering" management. "The head stormed down the corridor one day and screamed at me about the quality of the minutes of the departmental meeting," he says.
Mr A cannot understand why the head wants to hold on to him and is perplexed by the lack of action from the council, which he says is aware of the head's record. "I am more than unfairly treated, I have been treated quite unprofessionally," he protests.