The government's targets and inspection regime is seriously damaging teachers' mental health, a new survey has found.
More than half of school staff surveyed by the Association of Teachers and Lecturers, said that increased work pressures had damaged their mental health.
A majority experienced stress, exhaustion, disturbed sleep patterns and anxiety.
Almost four-in-ten also noticed a rise in mental health issues among their colleagues over the past two years.
The survey found a culture of fear and stigma about reporting mental health problems.
More than two thirds of those surveyed said they had decided to hide their health problems from their employers.
Unions said the survey showed that teachers were being driven to the edge.
"This is no way to treat a profession that wants to do the best for the young people they teach," general secretary of the ATL, Mary Bousted said today.
"I think everyone suffers from stress. I think the issue for teachers is it's absolutely unrelenting from the moment you start until probably about 11 o'clock at night.
"The government's own research shows that teachers are now working on average 60 hours a week. They work the most unpaid overtime of any profession."
The ATL will use the findings to push for an overhaul of the Ofsted inspection regime.
"The whole discourse around Ofsted has changed," Bousted is expected to say today.
"The agency can no longer sail through insouciantly pretending that there's no problem with the quality control of its inspections, nor with its methodology."
The findings come after plans by Michael Gove to extend school days and cut holidays were rejected by the body appointed to assess them.
The School Teachers Review Body found in February that there was no need to extend teachers' hours as they already work well beyond their contracted hours.
A spokesperson for the Department for Education said teaching had never been "more attractive, more popular or more rewarding".
"We trust the professionalism of our head teachers to work with their staff to ensure they receive the support they need and to see that any issues are addressed," they added.