Teachers are quitting their jobs because of ill-health in a much greater proportion than employees in other demanding occupations, according to a survey sponsored by The TES.
And experienced staff are also effectively being forced out of posts by a salaries funding formula which "penalises" older teachers.
At a time of anxiety over recruitment and the quality of staff, these latest findings are further proof of the crisis facing teaching.
Last week The TES reported that a survey of almost 800 secondary and primary schools revealed that underfunding and the profession's tarnished image were having a devastating effect on recruitment.
Further analysis of the vacancies, reveals that teaching suffers high levels of ill-health and dissatisfaction compared with other demanding professions such as nursing.
The proportion of teachers leaving with no job to go to is also high compared to other occupations, suggesting that older teachers are less financially attractive to heads.
The TES-sponsored survey, by researchers at Brunel University, showed that in secondary schools 37.4 per cent of vacancies were due to ill-health retirement. In primary schools the figure was 18.6 per cent.
Research compiled by the Institute for Employment Studies for the Royal College of Nursing two years ago revealed that of nurses who left a post, only 9 per cent were departing because of ill health.
Similar, earlier institute research, found that in banking and the pharmaceutial industry the figure was less than 5 per cent.
Teachers' leaders, psychologists and employment researchers cite stress as the key reason for such an exodus. Stephen Bevan, associate director of the Institute for Employment Studies research group, said: "There are a lot of applications for early retirement due to ill health among senior teachers and heads. There has been change upon change that can lead to a strong sense of feeling undervalued."
Mr Bevan, himself a qualified teacher and primary-school governor, called for greater attention by governing bodies to teachers' training and career development to help end feelings of "isolation and disempowerment".
The research report showed that of those leaving teaching posts at secondary schools, just 14.1 per cent had another post to go to. For those leaving a primary post the figure was 16.1 per cent. Institute research on nurses showed the comparable figure was 75 per cent; for the banking profession and pharmaceutical industry, 80 per cent.
Professor Alan Smithers, director of the Centre for Educational and Employment Research at Brunel and one of the authors of the report, said: "A lot of teachers are very worn out and tired with continually having to adjust. "
But the findings also mirrored the current school funding arrangements which meant heads viewed experienced staff as expensive.
Stress expert Professor Cary Cooper, an organisational psychologist at the University of Manchester Institute of Science and Technology, said teaching was now one of Britain's most stressful occupations.
Reduction of teachers' autonomy, more direct evaluation of their performance and the mis-match between experienced teachers' views of the job they entered compared to what it was now, all led to stress, he said.
Of those who left jobs with none to go to, he said: "They are probably burnt out and maybe feel the structural changes do not suit them. Many are saying: 'This is not the environment I want to work in'."
David Hart, general secretary of the National Association of Head Teachers, said: "The tragedy is that we are losing a significant number of experienced teachers. We cannot afford to lose them in the long term."