One out of every two teachers have been bullied at school - often by their headteachers, according to a survey.
Bullying happens in front of pupils
An Association of Teachers and Lecturers (ATL) study found half of those questioned had been bullied by parents, governors or headteachers.
Headteachers were said to be the bully in half of the incidents.
The union, which is holding its annual conference, is calling on the government to hold an inquiry into workplace bullying of teachers.
It says the types of bullying reported included continual unfair criticism, being shouted at in front of parents or pupils and the withholding of information.
One teacher from Kent told the union: "This headteacher didn't only single me out, she ruled every teacher by fear to the extent that teachers left in droves as she tried to build her empire."
I would like to see the perpetrators named and shamed
ATL member Sandra Douglas
Sandra Douglas, of the ATL, is putting forward a resolution to the annual conference calling for the education department to investigate the problem.
She said: "I am saddened but not surprised by the results of the survey.
"We regularly see the devastating effect that workplace bullying has on victims and their families.
"Better procedures are needed to deal with bullies and protect hard-pressed teachers.
"I would like to see the perpetrators named and shamed."