Headteacher jobs are still going unfilled because of a chronic shortage of talent willing to take on the top job, according to a major new staff-supply report.
Government policies still exacerbate the succession crisis, it also warns, with budget cuts and high workload forcing school leaders to retire early.
The report reveals that new mandatory headship qualifications are also affecting numbers applying for jobs, and governors say they are concerned by the poor quality of candidates they see at interviews.
The research, compiled for the Association of School and College Leaders and the National Association of Head Teachers, shows that even outstanding primaries and secondaries struggle to get more than two people to interviews. Schools who cannot find a quality candidate are increasingly appointing an acting head for a year.
Most vacancies for headteacher jobs attract fewer than 10 applications, and the number is is even lower in smaller schools.
Many current heads told researchers they quit after being asked to take on teaching commitments, or because they wanted to save their school money by giving them the opportunity to appoint a cheaper, younger successor.
Governors and teachers have also expressed concerns about the new National Professional Qualification for Headship (NPQH), now mandatory for new heads, saying it limited both the number of applicants and the number shortlisted.
The report also shows measures to reduce the workload of headteachers are not making the job more attractive. Many of those who responded to the survey said they were appointing because their head "had had enough" and was even willing to take a pension cut to avoid another year in the job.
Retirement is still the biggest reason for heads leaving, but 32 per cent still leave their jobs early. Governors told researchers - from The TES's sister company Education Data Surveys (EDS) - that this was because of pressure and a heavy workload, as well as projected financial problems next year.
"The head is retiring because of a budget crisis that would lead to a teaching commitment," one primary school said.
"The newly appointed, cheaper head faces a projected deficit budget from 2010 and at least a 50 per cent fall in the number of teachers on roll (to 123) from September 2009."
The number of mid-sized schools receiving 10 or fewer applications is now 90 per cent - the highest number ever recorded, something EDS describes as "concerning". Smaller schools receive, on average, four applications.
Governors described their concerns about the lack of interest in posts.
"This is an outstanding school (Ofsted 2006), but only two people applied. The successful candidate was the deputy head," one said.
Another outstanding school had to re-advertise four times, while other governors criticised their local authority's lack of preparation for succession planning.
Surveys by the National College for Leadership of Schools and Children's Services show an increasing interest in headship, up to 35 per cent among teachers in 2008. But the EDS report concludes the number of schools getting five or even fewer applications has once again climbed - suggesting that deputy and assistant heads lose their enthusiasm.
"It is one thing being asked whether you aspire to headship as a new teacher and quite another when faced with the reality of joining the leadership team as the next career move," EDS managing director John Howson said.
"The fact that we also recorded a downward trend in applications for many secondary schools at the deputy headship level means that more work may remain to be done in succession planning for headship to ensure sufficient talented candidates are always available."
Schools who responded to the survey were particularly critical of the NPQH, which they said had meant a dramatic reduction in the numbers applying for jobs.
"The requirement for NPQH is unnecessary and unhelpful for small schools, which is why we have a crisis with low applicant numbers. This is ridiculous," one said.
What the report describes as a "significant" number of secondaries are now offering heads salaries of over #163;100,000 - analysis of advertisements puts the figure at 15-20 per cent. It says this means the leadership scale for pay is increasingly becoming just advisory.
The number of "baby boomer" heads aged 54 to 59 remains at 25 per cent, the same as 2008. They are mostly due to retire before 2012 and EDS's John Howson said the concentration of the recruitment process into just three months was causing difficulties.
The local area is still the most significant recruiting ground for governors, as candidates now rarely seem to apply out of their travel-to-work area.
Headteacher vacancies were reported unfilled after an advertisement this year in some 19 per cent of secondaries, 26 per cent of primaries, and 27 per cent of special schools.
Last year, the percentages were 32 per cent for primary schools, 21 per cent for secondary schools and 38 per cent for special schools.
About 3,000 schools advertised for a headteacher in the past year.
The percentage of women appointed to headships in the secondary sector was nearly 44 per cent. This represents a significant increase both on last year's figure (31 per cent) and on the average for the past five years (37 per cent). Primary and special schools both appoint substantially more women than men as headteachers.
The average shortlist for headteacher posts in the primary sector was just three candidates.
HEADS GONE MISSING: THIS YEAR'S UNFILLED VACANCIES (AFTER ADVERTISING)
27%: special schools
These are trying times, but we are making headway - Steve Munby, chief executive, National College for Leadership of Schools and Children's Services
Like any major appointment, choosing a headteacher is a big decision and it takes time to find the right person for the job. It is not about getting it right first time, it is about getting it right for the long term. Re-advertisement need not be a bad thing.
I am encouraged to see that more women are being appointed to headship in the secondary sector. I am also pleased that the number of unfilled headship vacancies is down on last year. These are both positive signs, but we should not forget we are operating in unprecedented times.
This is a vital time to be a head. Economic factors are pulling on resources and schools are having to think even more carefully about how they will respond to the austere times ahead. This requires strong leadership and a pool of talent that can be relied upon for generations to come.
The National College is here to support all school leaders and our relentless focus will continue to ensure a steady supply of the very best heads.
A smaller number of applicants should not set alarm bells ringing providing they are the right candidates. Our re-designed NPQH, with a focus on those who are 12-18 months from headship, is ensuring that only those with a real commitment apply to the programme - and, more importantly, apply for headship.
In excess of 4,600 took the qualification last year and we are looking forward to welcoming more aspiring heads every year from now on. I know there is more to do if we are going to see vacancy rates continue to fall. I am certainly prepared for that challenge and I know every new head is ready, too.