Primary schools have long had problems finding new headteachers, but now the problem is spreading to secondaries.

Vacancies for secondary headships are at their highest since 1997 - the year when changes to pension rules prompted a rush for early retirement.

With 81 jobs advertised in January alone, according to analyst Professor John Howson of Education Data Services, vacancies are up 20 per cent on last year, and more than 50 per cent up on 2000. Professor Howson expects the figure to exceed 100 within two years. Roughly one in five posts needs to be re-advertised.

The increase is matched by a growth in six-figure salaries - and no longer just in London. Of three jobs offering pound;100,000 in January, one was in Kent and another in Liverpool. “The question is, who will be the first to break pound;130,000?” Professor Howson says.

Neil Davies, chairman of the National Governors’ Council, says recruitment has become “a nightmare”. Some schools are said to be getting no applicants at all. “I’ve heard that a number of times and it’s very alarming,” he says.

So how did such shortages arise in a job once considered to be the pinnacle of the teaching profession? It is partly a matter of numbers. Up to half of all secondary heads are due to retire over the next 10 years, but low recruitment in the 1980s - prompted by shrinking school rolls in the post-baby-boom decade -has meant there is no one following on, Professor Howson says.

“Schools are competing for a diminishing pool. We’re missing people in their late 30s and early 40s - that’s where you draw your new heads from.”

Local education authorities point to the large numbers of deputies also in their 50s, who have no interest in stepping up to the top job. At the same time, improved pay and new grades such as Advanced Skills Teacher have proved almost too successful in keeping younger teachers in the classroom.

Then there is the burgeoning private sector, now institutionalised into the education system. The growing consultancies and advisory positions offering one last career shift, one final challenge - and a healthy wad of cash to boot - are all too appealing.

John Dunford, general secretary of the Secondary Heads’ Association, says the feedback from many of SHA’s deputy and assistant heads is that the job of head is now “too high-risk”. The problem affects successful and struggling schools.

“What might be regarded as the best headships do not attract a very large field of applicants,” he said. “If a school is doing relatively well, it may be difficult to raise performance as much as expected. And in a school that’s not doing so well, the size of the challenge isn’t worth the difference in salary.”

The National Professional Qualification for Headship is supposed to encourage people up the ladder by preparing them for the leadership role.

But there is scepticism about how successful it has been.

Professor Howson notes a trend for significant numbers of NPQH graduates to get jobs as deputy heads rather than the top job. “They may go on to headships later, but if significant numbers are dropping out at that stage, the National College for School Leadership needs to train more people,” he says.

Mr Dunford echoes the point: “The NPQH is a good qualification, but I don’t think it’s made any difference to the numbers.” Others say the need to be at least enrolled on the course means some potential heads are barred from applying for jobs.

In fact, the NCSL’s own tracking survey of NPQH graduates suggests that only one in 10 decides not to become a head. However, two years after completing the qualification, only half of the rest are headteachers (including a handful as acting heads). The rest are “actively seeking” headships.

The NCSL has now commissioned a two-year study into best practice in recruiting and selecting headteachers. Dr Martin Coles, acting director of research, says there are already examples of good practice but many school governing bodies may be taking an unrealistic view when appointing heads.

He added that many fail to realise it’s a two-way process - “You’re not just choosing a head; the head is choosing you” - while too many are looking for Mr or Ms Perfect. “They have a generic job description rather than one that fits where the school is at. But a school might need different people at different points in its development or in their particular context.”

Last term the NCSL published a six-point action plan to help schools bring on their own future leaders - to “grow their own”. Industry and business - and other public sector services such as health - have well-established practices for bringing on the next generation of leaders. But in education, it has largely been left to self-motivated individuals to push their way up.

NCSL assistant director Jane Creacy says there is a need to appeal to schools’ enlightened self-interest as well as their sense of responsibility to the education system. “Everybody has a part to play in this,” she says.

“A healthy system grows its own future, its own leaders of tomorrow.”

The Growing Tomorrow’s School Leaders programme identifies six steps: schools need to develop an ethos where professional development and leadership are encouraged; they should audit their current practice; and then define the leadership qualities they need to nurture. Then they should identify groups of potential leaders; assess their individual potential; and finally help them grow into leaders by, for example, giving them opportunities to take charge of areas within the school.

There is a role for others outside schools to play. The NCSL found that formal planning systems “hardly exist” at LEA level. But there are signs at last that frustration at the lack of candidates is now prompting action. In Hertfordshire, where three of the eight secondary head-teacher vacancies last year had to be re-advertised, the LEA is resurrecting its own headship training programme - dropped when the NPQH was launched.

Stephen Lavender, Hertfordshire’s lead adviser for teacher recruitment and retention, says the LEA has written to all its secondary schools, inviting them to nominate a deputy head for an NPQH-style course.

The course offers training and support in areas where they lack experience, such as financial planning. It includes advice on working with governors and giving presentations - Hertfordshire found many deputies have little contact with their governing boards.

Meanwhile, the county is giving an extra push to talented deputies who are reluctant to seek promotion by putting some into acting headship roles.

Once they have had a taste, Mr Lavender says, many find they like it and apply for permanent posts.

And of course there is the question of money. “When a head resigns or retires, governors will often try to offer the next head the same salary,” Mr Lavender says. “We’re trying to advise them they need to review it and ask whether they’ll get someone good enough for what they’re offering.”

Growing your own may be a risky business: train up your rising star and watch them get poached by another school. But with Neil Davies at the National Governors’ Council also reporting a dearth of candidates for middle management posts, it may become an imperative.

“If we don’t get the people through as faculty heads or department heads, where are we going to get headteachers from in 10 years’ time?” he asks.

Time to start planting.