Just how do you attract a good head?
With the number of teachers reaching retirement age expected to peak in England next year, schools are going to find it harder than ever to recruit suitable headteachers. But we are not alone.
Attracting talented leaders is a global problem that needs urgent action as schools face ever more complex challenges - from managing greater autonomy, diverse immigrant intakes, and changing labour markets caused by globalisation, to meeting the need to mesh with the wider community.
"In many countries, the men and women who run schools are overburdened, underpaid and near retirement, and there are few people lining up for their jobs," says a report on improving school leadership by the Organisation for Economic Co-operation and Development (OECD).
Its study of 22 developed countries also found that the roles and responsibilities of headteachers and principals have expanded dramatically recently, and that most countries experience difficulty finding suitable candidates.
Beatriz Pont, co-author with Deborah Nusche and Hunter Moorman of the report, Improving School Leadership, Policy and Practice, says: "There is a general trend towards school leadership jobs not being as fully recognised as they should be. In many countries, wages do not reflect the job. Often it is a 60-hour working week and principals earn only 20 per cent more than a teacher, who has a shorter week and less stress."
The report says headship is an attractive proposition, so long as roles are clearly defined and leaders are given adequate autonomy. Leadership should be distributed, "not be a one man or one woman show".
It also recommends specific training, and says headship needs to become a more attractive job, with rigorous recruitment to unearth talent, and its own salary structure. A relative difference between teacher and heads' pay "can influence the supply of high quality candidates," the report says.
In England, heads' pay has been surging ahead, but in Hungary it is only around 10 per cent higher than teachers'. In Norway, heads' salaries are similar to those of highly qualified teachers. In Portugal and South Korea, remuneration does not distinguish between heads and teachers. Seniority is the only criterion, so some heads have lower salaries than the senior teachers they lead.
Performance-related pay can motivate potential leaders, but the external intervention required to assess performance is seen as "controlling" and may discourage a co-operative school climate, according to the OECD.
In France and New Zealand, leaders of "difficult" schools receive higher pay. And in Sweden, higher salaries are offered in regions where candidates for headship are scarce.
The OECD believes that "recruitment processes can have a strong impact on school leadership quality", and that there is a need to develop potential leaders earlier in their careers. Most countries, except France, have open recruitment. But, in practice, candidates from within the school have an advantage, which restricts the talent pool.
"Eligibility criteria need to be broadened to reduce the weight accorded to seniority, and to attract younger, dynamic candidates with different backgrounds," the report says.
In parts of Belgium, professional school boards or governors oversee school leaders, including their selection, and provide another layer of leadership. In Portugal and parts of Germany, heads are elected by their peers on a "first among equals" basis. But in most countries, recruiters have little or no training for the task. In England, "gut feeling" often predominates. The OECD recommends that recruitment should be professionalised.
This is happening in a limited way. Australia provides detailed guidelines to selection panels, while in Belgium, recruitment panels consist of external members, such as other school principals or business managers, for a more objective view. At the other end of the scale, Swedish panels include teachers from the recruiting school, and sometimes students as well.
Many countries simply rely on a candidate's interview. Austria, Hungary, Chile and Spain also require candidates to present proposals for the schools they want to lead.
While the biggest issue for many countries is the lack of applicants for top posts, the quality of heads is rising swiftly up the agenda, due in part to increased autonomy over curriculum, hiring, and finances.
Ms Pont says: "There is a trend in the OECD to decentralise and for schools to have greater autonomy. The general belief is that the closer the school is to the demands of society, the better they will respond to them." But this has added to the demands on heads, as has the need to deal with constant change.
"School autonomy alone does not automatically lead to improved leadership," the report says. In this new environment where heads must be multi-skilled, clearly defined roles will prevent overload. Some countries have sought to tackle this by hiring heads from outside education. But "the private sector is not a paragon of effectiveness", warns the OECD.
Many countries have stepped up leadership training. This is mostly in-service, but in Austria heads must complete compulsory management training for their provisional contract to be extended. Its leadership academy, established three years ago, has already trained some 40 per cent of the country's targeted 3,000 school leaders.
The aim of Austrian and Australian school leadership institutes is to equip leaders with the skills to push through deep-seated education reforms at school level.
Ms Pont says: "Australia has defined a blueprint for systemic school reform, with school leadership at its core." The more government initiatives there are, the greater the need for a small group of managers to carry them out.
Chile, which is also undergoing major reforms, has borrowed heavily from the UK's National College for School Leadership. England is considered relatively strong on leadership training, says Ms Pont. But no country excels in this area.
Nordic countries prefer a more participatory approach, particularly in Finland (see panel, left), with teachers learning alongside heads in an "apprenticeship" model.
Given Finland's position at the top of international school performance league tables, such approaches cannot be ignored even if they are not fashionable.
The OECD agrees the best solutions appear to be those developed locally to meet specific needs, and that includes Finland's credo: if you recruit the best people to be teachers, you will find the best school leaders among them.