A growing number of headteachers are being forced to put off retirement and take on responsibility for more than one school, new figures suggest.
The annual statistics digest of the General Teaching Council for Wales (GTCW) reveals the changing face of school leadership in Wales and highlights growing fears of a recruitment crisis.
In 2008, just eight heads were in charge of more than one school, but in March this year that figure stood at 39, including one who headed three institutions.
The number of school leaders working into their sixties has also grown steadily, with 123 heads aged over 60 in March this year, compared to 91 in 2009. According to the statistics, four headteachers currently in service are aged over 65.
Anna Brychan, director of the National Association of Head Teachers Cymru, said: "Recruiting heads isn't easy any more because the school leadership role is much more complex than it has been in the past. Local authorities are finding it difficult to appoint, so they are increasingly federating schools under a single head and asking those facing retirement to stay on a little longer."
Economic uncertainty, especially over pensions, could also be forcing some heads to work longer than they had intended, she added.
Gareth Jones, secretary of the Association of School and College Leaders Cymru, said: "The size of the field of candidates for a headship post is much smaller than it was a decade ago. Because of the growing pressures of the job people are asking themselves if it is really worth it."
The Welsh Government said that although many teachers hold the National Professional Qualification for Headship (NPQH) and are eligible to apply for headship, it recognises there can be fewer applicants for posts in some rural areas and in certain sectors.
The Government is currently in the process of reforming the NPQH and said it is working with local authorities to match candidates with the demand for heads. A spokesman said it is a matter of personal choice whether heads remain in their post over the age of 60.
But Ms Brychan said the "dramatic rise" in the number of heads running more than one school was a serious cause for concern.
"Our fundamental position is that you need one head for one school," she said. "That way they are fully responsible to parents and governors and for inspection outcomes."
Mr Jones said more councils were choosing federations as a way to protect small schools from budget cuts.
Headteacher Huw Thomas, who has run two primary schools on Anglesey for more than a decade, said the pressure associated with running more than one school is one of the factors putting people off headship. "It is a very challenging position and it certainly wouldn't be everyone's cup of tea," he said.
Although Mr Thomas's schools, Ysgol Niwbwrch and Ysgol Dwyran, are in the process of federating, he has been running them under separate budgets and governing bodies since 2000. "I was the first in the authority in this position, so I had no one to learn from," he said. "But it's become a way of life."
A Welsh Government spokesman said: "Our policy is that schools need to work together more . From September 2012 it is planned that local authorities (as well as governing bodies) will have the power to create school federations.
"It is a natural progression in federations to have one headteacher with a unified leadership team."
Original headline: Heads kept in post as shortage bites deep