Ofsted inspections, bullying heads, disruptive pupils and overcrowded classrooms are causing severe stress in teachers and damaging their mental health, teachers' leaders said at their annual conference.

The National Union of Teachers voted to lobby Government on the issue, after responding to the findings of a working group it set up two years ago to investigate mental illness among teachers.

It found long hours, insufficient support from management, abuse from pupils and an excessive workload were all sources of stress that led half of all teachers to consider leaving the profession.

Research uncovered included evidence that the suicide rate among teachers is higher than average, and that half of ill health retirements are caused by stress or psychiatric illness.

Helen Andrews, who proposed a motion that extreme stress suffered by teachers should be tackled, told the event in Cardiff: "Originally we had issues such as class sizes, now it has been joined by Sats tests, performance [assessment], Ofsted, and management bullying.

"Schools under constant alert of Ofsted inspections frequently create unacceptable levels of stress which are passed on to all staff, and which can be sufficient to tip a teacher into mental illness."

It was seconded by John Illingworth who cited unmanageable workload, violence and disruptive monitoring as causes of stress. He said: "Disruption, anxiety and burn-out have become the teachers' disease, although they often remain hidden.

"Much is unreported or is in the guise of a physical ailment. Teachers are reluctant to admit they're not coping.

Teachers at the conference voted for recommendations including: "Whatever the inspection system in place, it [Ofsted] needs to examine the attitude of schools towards teacher mental health. It also needs to encourage schools to look after the well-being of their staff and not cause mental ill health through the manner in which inspections are carried out."

The motion added that leadership should "continue to press Government and employers to recognise the true extent of stress in the teaching profession, and to be more pro-active in tackling the problem of mental health conditions."

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