The teaching council says the high workload is an issue

The flow of leaders out of the system will peak over the next few years as the Baby Boom generation retires.

As part of the response, federations are a great way for groups of schools to work together to "grow their own" leaders, an expert says.

Other initiatives include flexible pension arrangements and changing teachers' perceptions of leadership.

The GTC's annual survey was severely compromised by a low response rate - only a quarter of the 10,000 in the sample responded.

So the results were skewed by an over-representation of female teachers in their 50s in primary schools.

That said, nearly a third (32%) envisaged moving into leadership or management posts other than headship, while 6% anticipated becoming a head teacher and 9% thought it probable that they would take the National Professional Qualification for Headship (NPQH).

The NPQH was made a mandatory requirement in 2004 for those seeking headship in England and Wales.

'Urgent'

The GTC's report said the male bias among school leadership looked set to continue.

The perception of leadership is often quite different from the reality when people experience it Chris Kirk National College for School Leadership

Chief executive Keith Bartley said the development and recruitment of high quality head teachers was an urgent issue.

"We urge that more needs to be done to ensure that the learning, expertise and inspiration of experienced head teachers is harnessed and passed on to those taking up headship positions.

"We must also invest in and encourage potential head teachers of the future to take their next steps."

He added: "Relieving the current administrative burden of the role will be a key part of achieving this."

Trend

To cope with the outflow of experienced heads the National College for School Leadership (NCSL) has been co-ordinating efforts to improve succession planning within schools.

The problem has undoubtedly been getting worse.

In 2004, some 2,250 leaders - heads, deputies and assistant heads - retired.

The NCSL estimates that in 2009 this retirement rate will have reached 3,500 and will stay at that level for several years before falling again.

The college's director of succession planning, Chris Kirk, said larger organisations tended to have human resources departments that would have some kind of plan for coping with that level of turnover.

But smaller organisations did not and just had to cope as best they could.

Issues differ

"Schools are a bit different: we can't just let them fall off a cliff," Mr Kirk said.

Having looked at the issue the college has concluded that the problems are common throughout the Western world but in fact the best solutions are those developed locally to meet specific needs.

This sounds like a cop-out but Mr Kirk said it arose from the nature of schools themselves.

"The issue for a small primary school is likely to be very different from developing the next head for a large specialist secondary school," he said.

"It probably has a very small leadership team, if any. Indeed, is it from that school you get your next head teacher?"

Likewise the experience of professional development of teaching staff that might lead them into headship varied from area to area, school to school and even teacher to teacher.

Talent pool

Although problems might be local, the NCSL had used pilot programmes to crystallise what appeared to work well, he said.

"In the longer term, there's a fantastic opportunity to get a culture of leadership talent development into the system like it has probably never known before," he said.

But the problem is more urgent.

A "headship index" produced for the first time recently by the college - and intended to become an annual survey - suggested that about a third of all teachers would like to become a head teacher.

And there is now a pool of about 10,000 teachers who have attained the NPQH but who are not head teachers (as well as about 13,000 who are), of whom some 40% are said to be actively seeking headship.

"So the ambition is there, and the numbers," Mr Kirk said.

He believed all those who aspired to headship could attain it - given the right support, mentoring, training in appointment interview techniques and perhaps internships.

"The perception of leadership is often quite different from the reality when people experience it.

"There's no doubt that it's challenging but it is also incredibly rewarding."

DIY leaders

A striking feature of the existing system was that some schools had the self-confidence to produce future leaders - without worrying that they moved on to other schools.

"There are some schools that just seem to turn out leader after leader after leader.

"They never have a problem, they are so good at growing their own."

Federations of schools could play a key role in this regard.

The Yewlands "family" of schools in Sheffield, for example, comprises a secondary school, five primaries and a special school.

It has subject directors - individuals who not only head, say, the music department in one school but across all the schools.

"The chances to develop leadership skills are clear to see," Mr Kirk said.

Yewlands School's head teacher, Angela Armytage, said: "What we have is a group of high level leaders who are really flying in terms of their professional development.

"They are working right across the piece, going into each other's schools, doing partnership teaching and putting in fantastic professional development days, for example for 350 staff.

"They are just so excited, they see opportunities for themselves - and not necessarily in the sector in which they started."

But does it not trouble her when these "home grown leaders" go off to work elsewhere?

"No, it doesn't bother me because what it is doing is giving us a very strong recruitment and retention package, so we are now finding we are attracting very high quality fields for posts."

Staying on

And another solution is to retain the school leaders who are already in place.

The GTC's annual survey provides little reassurance.

It says: "Retention of the teaching workforce has for a number of years been a concern at national and local levels. The results of the 2007 survey do little to allay these concerns."

There was no fall in the proportion of teachers looking to retire: 29% planning to go within five years, with head teachers once again foremost in signalling this.

"Indeed, more than half (56%) of the head teachers who answered the relevant item expected to retire in the next five years."

The NCSL realises that the quickest solution to a shortage of leaders is to persuade the ones you already have, not to leave.

Pension flexibility

There are various ways of doing this. Increasingly - though there are no firm statistics - heads have been offered job shares.

Sometimes a successor is recruited on the basis that they will share the job for, say, a year - after which the head will proceed to leave and the school will be theirs to run.

Flexible pension arrangements mean a head can drop down to four or three days a week, and draw their pension for the rest of the time. The NCSL is keen to raise teachers' awareness of this.

Efforts are being made to encourage more women and people from minority ethnic groups to come forward to stop the system "leaking talent".

Work is also being undertaken with school governors - who make headship appointments but tend to lack experience and may not cast the net widely enough.

Mr Kirk is optimistic that the problem can be tackled, and evidence from annual surveys of recruitment adverts suggests there has been some success in stemming the tide in secondary schools.

But with re-advertisements for primary school headship vacancies stubbornly high, there is also some way still to go.