"Stale headteachers" who have been at the same school for too long should be moved on, according to a parliamentary report.
In The Role of Headteachers, MPs on the education select committee said:
"We have noted evidence that there is a limit to the length of time that heads can continue to have a beneficial impact on their schools. "
The report, which followed a four-month investigation, said an appraisal process should be used to assess whether headteachers should be moved on. Appraisal should also be linked to performance-related pay for heads.
The committee had heard evidence from Professor Michael Barber, head of the Government's standards and effectiveness unit, that heads are most effective between their third and seventh years, and from Professor Peter Mortimore, of London University's Institute of Education who said seven years was the optimum time for a school's head to serve.
The cross-party committee was chaired by Margaret Hodge, since promoted to education junior minister.
While headteacher unions took issue with the concerns over "stale heads",they largely agreed with the views expressed in the report which said recruitment problems could be made worse if the National Professional Qualification for Headship became compulsory by 2002.
"In the light of difficulty in attracting candidates to the NPQH, we are concerned there is a danger of exacerbating recruiting difficulties," it said. There is a shortfall of 500 on the Goverment's target.
The committee said a mandatory qualification was desirable, but called for an overhaul of heads' training. It recommended an NPQH part I, for trainee headteachers, which differentiates between running secondary and primary schools, then NPQH part II, (replacing Headlamp) for serving heads,with a third programme for experienced heads.
They concluded that heads should have a background in teaching: "The overriding aim of the school leader must be to create a school environment which supports the best possible teaching and learning."
The changes in the heads' role in the past 10 years were recognised by the MPs. They said headteachers should be able to employ others to carry out some of their tasks - for example dealing with broken windows - and use outside consultants. However, this may be too expensive for many schools.
Schools should be able to appoint heads on fixed-termed contracts. These could be used to encourage "troubleshooting" heads to work in difficult schools. These contracts would carry an enhanced salary and could include meeting specific targets.