When Philippa Lee stood on the greenfield site where her new school was to be built, she knew two things. She was going to get a cracking school off the ground here in West Sussex - and after five years as its headteacher she would go.

“On the day it opened, people were saying to me: ‘What will you do after this?’ I was only in my thirties and, after all, in other walks of life people don’t spend 25 years in the same place any more,” she says.

That’s true, and new research suggests that the character of the portfolio careerist is now cropping up in headship too. These heads give a job five years or so and by the time they take their second headship - if there is a second one - they already have their exit strategy planned.

“I certainly had,” says Ms Lee, twice a head and now head of institutional frameworking for Becta, the British Educational Communications and Technology Agency. “I knew as soon as I went into teaching that I wanted to be a head, but I was only 31 when I got my first headship. The idea of never doing anything different didn’t appeal.

“There’s also the question of what skills you bring to a job. I don’t think I’m really a maintenance person. I’m more a strategy type. So setting up a new school from scratch with a new building and full set of appointments was my sort of thing, as was having a vision and realising it. Then it was time to move on.”

The portfolio head has come to light in research done by Alan Flintham, a consultant headteacher with Nottinghamshire education authority and a research associate with the National College for School Leadership.

But anyone with half an eye on schools knows that heads today often move on after five years or so. Headship as the acme of a long career is becoming a thing of the past for some.

What makes portfolio heads different, though, is that they leave headship for another career, rather than for another school. And that has huge implications for the future of education.

Alan Flintham is the first to admit there are no hard-and-fast statistics on portfolio heads, but he has detected more than 50 of them in his research into school leadership sustainability and he is convinced it is time to start making sure there is a supply of well-trained deputies ready to step into the gaps portfolio heads leave behind.

“The next generation needs upskilling while the portfolio head is still in place. So it should be possible to meet the developmental needs of the head while getting the potential heads ready,” he says.

Mr Flintham himself is on secondment from his headship of Quarrydale comprehensive in Sutton-in-Ashfield, Nottinghamshire.

“Secondments - say, not one day a week for a year but 30 school days in a chunk - give deputies a real chance to run a school. We need to provide that sort of cover, that sort of experience, to upgrade the deputy head to acting head for a while. It’s a great confidence-booster for those who are up-and-coming. My LEA seconded me for two years and my deputy is running the school.”

But doesn’t it go against the grain to invest in the training of heads who are likely to leave the job after just a few years? No, says Alan Flintham, the expertise gained in headship can still be fed back into schools. Many portfolio heads, such as Philippa Lee, whose Becta work includes helping headteachers to self-evaluate, simply move to a different part of education.

“When you’ve been a head, you realise that you have developed a wider range of skills than many other jobs give you: strategic, personnel, budgetary.

“It did occur to me that I could take those skills to industry,” she says.

“But the fact is I’m interested in making a difference to the education of children, and I’m still doing that. More and more people are going into their second headships keenly aware that the world of education is about more than just being in school.”

She does not rule out taking on another headship later, and says she would be especially tempted by another new school.

For the NCSL the problem of portfolio heads can be solved by one of its favourite phrases: distributed leadership. This means not running a one-man band and making sure your deputies and other management tiers have a crack of the whip too.

“We must now review how we can support those who are in headship for a short time, both to capture the positive changes they bring to schools, and to ensure pupils consistently benefit from strong school leadership,” says Geoff Southworth, director of research for the NCSL.

“It is clear that portfolio heads, practising a model of distributed leadership, which empowers middle and senior leaders, have the potential to provide a robust environment for learning and teaching.”

In other words, portfolio head is here - and then there. So the rest of the educational world has to get nippy too.

Alan Flintham’s research can be read in full at www.ncsl.org.ukresearchassociatesThe college also runs a consultant leader development programme which trains heads to groom their senior managers for headship; and it produces a distributed leadership pack to be used with a special section of its website: www.ncsl.org.uk