The survey involved 852 primary and secondary teachers from 17 schools between January 2006 and this August. Based on their responses to questions on the state of their psychological health, the foundation classified 23 per cent of respondents as psychologically disturbed.

With 52,000 teachers in Hong Kong, Samantha Yung Yuen-man, clinical psychologist with the Whole Person Development Institute, projected that around 12,000 serving teachers were emotionally disturbed.

The findings echo those released by the Professional Teachers' Union and Chinese University's Institute of Asia-Pacific Studies. Their poll of 2,104 teachers in mid-July found that nearly nine out of 10 respondents felt very stressed at work and one in 10 appeared to have an anxiety disorder.

Union president Cheung Man-kwong said the 'shocking situation' had gone on for a long time.

'The whopping statistics revealed that teachers are under tremendous stress due to the current wave of school closures. They are in persistent fear about their future prospects,' he said.

Denise Tsang Law Mei-chi, senior clinical psychologist with Castle Peak Hospital, said burnt-out teachers visited their outpatient clinic for help.

'In the most serious case, the patient had to suspend teaching for a semester,' she said.

Wong Kwan-yu, chairman of the Federation of Education Workers, said the workload faced by teachers overseas was much less than in Hong Kong.

'I went to the UK and Sweden several years ago, where teachers' main duty is teaching. They don't have to get themselves involved in other duties like administrative work and extra-curricular activities,' he said.

The thorough nature of local education reform was another big difference from overseas, Mr Wong said.

'Hong Kong education reform is reputed to be the world's biggest,' he said. 'Overseas, reform involves curriculum changes, but the current reform involves revamping the academic structure and exam format, which entails across-the-board changes to subject arrangement and the inclusion of school-based assessment.

'Teachers also need to deal with other initiatives like the implementation of school-based management, internal and external reviews, and the adjustments to the medium-of- instruction policy.'

Ho Tai-on, a biology teacher, said the pressure he had endured at his former school was excruciating.

'That was a low-banding school in Kwai Tsing District,' he said.

'Due to low enrolment, the pall of possible closure loomed over the whole school. To make sure Form One students would not switch to another school after registration in July, we had to organise a 10-day orientation camp for them in summer ... To ensure we wouldn't get panned in students' appraisals of teachers, we had to pander to them. There were also targets to meet for boosting public-exam pass rates.'

Ng Wai-choi, a discipline master of AD&FD POHL Leung Sing Tak School in Yuen Long, said he felt guilty when his administrative work overwhelmed his teaching duties.

'As I can't devote more time to teaching, I feel indebted to my students,' he said.

'The feeling of guilt weighed on me so much that I went to talk to my principal about giving up my post of discipline master and going back to full-time teaching so that I can concentrate on nurturing my charges.'

Chan Chi-hung, principal of the Yuen Long primary school, said the heavy workload had snuffed out many teachers' passion for the job.

'Some even ponder whether they should leave the profession altogether,' he said.