According to the register kept by the General Teaching Council for Wales, 92 out of 222 secondary heads in Wales are aged 55 or over and likely to retire within the next five years before they reach 65. That is a significant turnover.
Further research by the GTCW indicates that of 279 registered deputy heads, only 102 have gained the National Professional Qualification for Headship, now mandatory in Wales. Some 200 assistant heads and other secondary school staff have gained the NPQH but few have essential experience.
Given the ratio of potential candidates and vacancies, the promotion prospects for the job hunters look good. However, the prospects for governors seeking to recruit the best candidates are less positive.
The larger schools and those in the more affluent areas will continue to attract candidates for headship but smaller schools, and certainly those in what may be described as the more challenging settings, will find it increasingly difficult to attract any applications at all, let alone strong candidates.
Most of these deputy heads are members of the Association of School and College Leaders Cymru and they are saying that not all of them are keen to apply for headship posts, now or in the future.
Leading and managing a community of 100 adults and some 1,000 young adults has always been challenging and requires many skills and personal attributes, the management of people and relationships being one, if not the most important.
The next few years will bring additional demands upon heads as schools try to cope with the financial consequences of falling rolls as well as the implementation of significant curriculum change.
The flow or should that be tsunami of consultations and guidance documents, with 18 of the latter due to be published in the autumn term alone, does little to reassure potential candidates that there will be time for a life outside of school.
Another factor in this reluctance to step up to the challenge is the ever increasing burden of responsibility being placed on heads with no consequential increase in the resources to fulfil them.
As John Dunford, general secretary of the ASCL, has put it: "There should not be extra responsibility without the extra resources to fulfil them."
A number of deputy heads, in response to my questions as to possible headship, have responded with: "As a deputy I have much of the decision-making power of the head in the day-to-day running of the school but without the final responsibility if things go wrong.
"Do I really need the hassle involved in being a head?"
But in my view there can be no other job that offers the opportunity to steer the direction of a sizeable institution and influence the lives of so many young people.
In between all the government initiatives and other pressures, there is still the space to be creative and create opportunities for young people that set them on the road to success in life.
Heads have a key role in the provision of a high standard of education to the young and in the fostering of the community dimension and we cannot afford to leave it to chance as to whether potential future heads feel able and willing to take on the challenge. It is a matter of some urgency that we need to focus on the issue of succession planning and that starts with developing the leadership and management skills of the current generation of middle managers who are the source of future heads.
In the meantime, governors and the Assembly government would be wise to take care of our current leaders so that they do not leave even earlier than planned.