And it is pressure from parents which may be driving them out of the job, a questionnaire completed by more than 2,650 teachers in Cheshire suggests.
The study, carried out by the education authority, found that 987 teachers were seriously considering leaving within five years.
Only half were over 50, while a fifth were under 34.
David Cracknell, Cheshire's director of education, said: "A haemorrhage on this scale for the younger and middle years of the workforce will be unsustainable."
Asked what could improve their profession, 97 per cent of those surveyed cited "improved parental attitudes", ranking it as a concern equal to excessive paperwork for causing teachers stress.
Mr Cracknell said parents were increasingly likely to write letters of complaint to teachers.
"Teachers see themselves as working extremely hard, and then getting it in the neck if a child underperforms in a parent's eyes, even if the teacher has done their best with that child."
Only 15 per cent o "leavers" said teaching was a respected profession, though 83 per cent had believed that it had been when they were starting their careers.
Disillusionment appeared to be worse in the primary sector, where 77 per cent of heads said morale had diminished over the past decade.
Margaret Morrissey, from the National Confederation of Parent Teacher Associations, said: "With schools encouraged to have their own marketing strategy, a presence on the web, and the advent of league tables, it is to be expected that parents see themselves as consumers."
A study of London teachers, published earlier this year, revealed a comparable proportion in the capital also wanted to leave teaching.
Several other local authorities also reported evidence of rises in the numbers leaving teaching.
Bournemouth reported a 16 per cent rise in the number of teachers leaving the authority this summer.
And Wolverhampton said there had been a "worrying increase" in the numbers leaving the profession.
Government statistics show that 224,000 qualified teachers left the service between 1993 and 1998, but only 77,100 retired.