Almost half of the London heads and deputies who have quit or who are leaving their posts this year will go early - with more than a quarter of them taking ill-health retirement, a survey reveals this week.
It discloses high levels of unhappiness with governing bodies and the Office for Standards in Education, with heads and deputies suffering overload and working upwards of 51 hours a week.
More than a third of 149 respondents to the survey by the National Association of Head Teachers said OFSTED played a major part in their decision to leave either pre or post-inspection.
Other reasons cited by heads and deputies for leaving were deteriorating health (other than ill-health retirement), management of a constantly changing curriculum, and having to deal with aggressive parents and pupils.
Eight out of 10 respondents said pupil behaviour had deteriorated in the past three years and many believed they were not supported by parents in their attempts to manage bad behaviour.
Schools in London already have serious problems recruiting headteachers, with more than four out of 10 posts not filled at the first attempt.
And David Hart, NAHT general secretary, warned that many schools in the capital would now be without permanent headteachers at a time when they desperately needed stability.
"One of the first challenges facing the new government will be the need to stop this haemorrhage of talents, otherwise it will do incalculable harm to the drive to raise standards," he added.
The survey by the NAHT comes just a week after the revelation in last week's TES that resignations among primary school heads had hit record levels. That issue contained more than 175 advertisements for primary heads, on top of 168 the previous week. This compared with 138 and 61 for the equivalent weeks last year.
Vacancies in the first three months of this year were also at a record high, up almost a third compared with the same period last year.
The record levels of resignations are believed to have been triggered by ministers' attempts to cut the number of early retirements.
Official figures for the number of teachers leaving the profession before the early retirement scheme was tightened up are not yet available, but unions estimate that as many as 17,000 could have gone at Easter.
Teacher Training Agency statistics already reveal a crisis in recruitment of graduates willing to train as secondary design and technology teachers. Only 250 out of 900 places on PGCE courses for this September have been filled.
* Technology Extra, TES2, centre pages