Schools are still struggling to find new heads and deputies, with half of primaries receiving five or fewer applications for the top job, according to a new survey.
The two headteacher associations, which commissioned the report, say comparatively low pay, the funding crisis, red tape and overwork are to blame.
The figures, based on returns from 2,500 schools in England and Wales, show that recruiting secondary heads has become a little easier since last year.
But even so, slightly more secondaries failed to make an appointment after advertising a headship, while special schools averaged only 3.6 applications.
The situation could get worse as more teachers near retirement age said John Howson, director of Education Data Services, who compiled the figures for the National Association of Head Teachers and the Secondary Heads Association.
David Hart, NAHT general secretary, said: "The number of applicants for head and deputy headship posts is running dangerously low.
"Matters have been made worse by the funding crisis, continuing excessive bureaucracy and workload and by over-ambitious government demands to raise standards."
John Dunford of SHA, added: "Until there is a more intelligent accountability mechanism for headteachers and pay rates comparable with similar jobs in other sectors, there will continue to be too few people willing to take on the immense responsibilities of headship."
Catholic schools and schools in London fared particularly badly: those in the capital were more likely to appoint an internal candidate. Women accounted for most new appointments in primaries but men were in the majority in secondary headships.
Only 51 out of 2,000 people appointed heads, deputies or assistant heads were from ethnic minorities. Meanwhile, government guidance which says heads should be responsible for staff appointments outside the leadership group has been criticised by governors.
The guidance says governors should delegate this responsibility to headteachers "unless there are good grounds not to do so". However, the underpinning regulations say only that governors "may" decide to delegate.
Governor organisations have been fighting the move since it was proposed in 2000.
Stephen Adamson, acting general secretary of the National Association of Governors and Managers, said: "This is the worst of both worlds. On the one hand, the Government says staffing is a governor responsibility, and on the other not to exercise it."
Brian Weller, of the National Governors' Council, said: "We have not met many headteachers, particularly in primary, who are keen to divest themselves of governor involvement in appointments."