Two-thirds of education authorities in England and Wales are finding it increasingly difficult to recruit headteachers, a TES survey suggests.
The survey of authorities in England and Wales provides extra evidence that a shortage of good school leaders is forcing schools to share heads through federations or other collaborative arrangements. Of 42 authorities that gave a view, 27 indicated they were finding head recruitment more difficult.
Schools face a demographic time bomb with 45 per cent of England's 25,000 heads aged over 50 and due to retire by 2014, according to National College for School Leadership research.
The TES survey found the shortage is being exacerbated by early retirements; 37 per cent of the heads leaving their schools at the end of term are also quitting the profession before the normal retirement age.
Staff are also increasingly reluctant to take the top job. A leadership college study of senior staff in Bromley, south London found three-quarters of assistant and deputy heads did not want to become heads.
This echoes a report for the General Teaching Council for England which said becoming a head was low on the list of most teachers' priorities. Out of 4,184 teachers questioned, 57 per cent said they were unlikely to consider applying for the top school jobs in the next five years.
Recruitment expert John Howson, of Education Data Surveys, has found that the problem is not just a lack of candidates, but a lack of quality.
Early returns from a report he is compiling for the headteacher unions showed that, of 380 primaries that had failed to appoint heads, 250 had done so because none of their applicants had been good enough.
The result is that many schools are having to use acting heads or share their leaders with other schools. The TES survey found that 2.6 per cent of schools in the 49 authorities responding expected to start next term without a permanent, dedicated head. In Rutland, the figure rose to 19 per cent.
If the overall average were reproduced throughout England and Wales then some 640 schools would be expected to be without their own heads in September.
Tim Benson, who represents the National Association of Head Teachers'
national council on a joint leadership college working party on head recruitment, said: "A school without a leader begins to founder. I can't see any school being successful in the long term with someone just popping in to advise."
He is worried that the Government now sees putting a single head in charge of a federation of schools as the solution. The TES revealed last month that Kent - England's biggest authority - had warned that with the number of acting headships rising from 23 to nearly 50 in less than two years it was considering federations instead of automatically appointing new heads.
This week's survey shows that Somerset, West Sussex, Wiltshire, Rutland and Ceredigion in Wales are among the authorities that have already introduced federations or collaborations under shared heads as a solution to head shortages.
However, a report compiled by the leadership college found that creating more "executive headteachers" - as it calls leaders of more than one school - was not necessarily the answer.
Its interviews with eight of the 25 executive headteachers in England said using them was a "constructive and powerful" way of leading a school, particularly when a successful head is asked to help turn around a struggling neighbour.
But the shortage of exceptional heads, with the strength and character to meet the demands of leading two or more schools meant that the model was not a panacea.
"Questions remain about how appropriate or feasible it would be to apply this model widely," it said. "Given the characteristics of the heads we interviewed, it seems likely that there would be a limited number of such leaders who could expand their responsibilities in this way."
The survey revealed a patchy picture, with shire counties that have a large number of small primaries reporting particular problems. Urban authorities, including the London boroughs of Merton, Southwark and Greenwich, also noted difficulties.
But other areas, such as Sunderland, Stockton, and Redcar and Cleveland in the North-East; Sandwell in the West Midlands and Tameside in the North-west, reported no problems.
Reasons cited for the difficulties in recruiting heads include the minimal extra salary they receive for the extra responsibility that goes with the job, workload, pupil behaviour, a lack of resources and government initiatives such as workforce remodelling.