How long does it really take for a new head to make an impact in a school? Is there an optimum length of time to stay as head in the same school? Is it good for the head, as well as the school, to remain beyond a certain length of time?

There are, in fact, surprisingly few recent studies into these important aspects of school and professional development. The era of failing schools, into which the super-hero head is parachuted to save the school before dashing on to his or her next mission impossible, has helped to focus attention on this issue. But it has also heightened the sense of guilt and unease many long-serving (but no less effective) heads have felt for staying put, rather than moving on.

It was instructive, therefore, at last year’s annual conference of the Association of School and College Leaders to witness the almost palpable sense of relief among seasoned heads in the audience, when they were told by Professor Andy Hargreaves of the Lynch school of education, in Boston, that bringing about real and lasting change in schools takes time.

“Sustainable leadership” involves (among other things) staying the course.

It is not therefore surprising to find the ASCL, in its evidence to the PriceWaterhouseCooper’s review of school leadership, stating that it “supports the notion of headteachers remaining at least five years in a school”. The concept is captured neatly in the ASCL publication by Robert Hill called Leadership that lasts.

Although it is impossible to put a precise figure on it, many heads would agree (intuitively) that a five-year stint is the minimum time needed to bring about any meaningful change. But is there also a maximum length of time for leading the same school, beyond which the law of diminishing returns kicks in (both for the head and the school)?

It was with the aim of putting some quantitative flesh on the bones of intuition that heads of HMC schools were recently surveyed. Some 200 members responded (80 per cent of the membership).

Of these three-quarters had been a head for five or more years in the same school, while two-fifths had been a head for 10 or more years in the same school. The advantages for themselves, as individuals, were seen as:

* familiarity (knowing the people, the place, the issues, the local community in depth)

* building lasting relationships (with governors, staff, parents, pupils, the community)

* continuity (seeing ideasplans come to fruition, seeing at least one cohort of pupils through the school, one inspection cycle etc)

* introducing significant (long term) change (and reaping the rewards)

* stability (particularly for spouse and children).

The main disadvantages cited were becoming stale (complacent, bored, less energetic, less ambitious etc) and having to live with the mistakesconsequences of previous big decisions. Responses depended on age and length of time in headship (with greater anxiety shown when approaching 10 years in the same post). There was no shortage of practical considerations (“can’t use speeches and talks again”) or comical responses (“no hairgrey hair!”).

But, for schools too, long service offers considerable attractions. An article in The TES last June featured one Somerset head who, on his first day in the job, vowed to stay in post for at least five years. Andy Russell, the head in question, told the governing body, which appointed him: “If I haven’t done the job in that time, then I’m not fit to be here.”

Toby Salt, strategic director for leadership development at the National College for School Leadership, is also quoted in the same article as saying: “You can have an impact on some things - such as behaviour - quite quickly, but fundamental change takes time.

“We need to beware the danger of quick wins - the effects of the hero head are too short-lived - and focus on strategies for long-term gain.”

The message is clear: sustainable change is essential. Sustainable leadership may well be the key. But it, too, needs nurturing and feeding.

This then takes us back to sabbaticals, also a key ASCL recommendation to the PWC review. A subsidiary strand of the survey of HMC heads referred to above asked about sabbaticals. Of those surveyed almost a fifth had received a sabbatical (all of these being heads with five or more years service, whether in their current or previous school). The sabbaticals ranged from half-a-term (the minimum) to a year (the maximum); the most common sabbatical lasted for a term.

Surely this is one area where the Government could learn from the independent sector, without the latter appearing to be patronising in any way? Remaining a head and sustaining meaningful change requires both give and take. A serious commitment to heads’ work-life balance by governors means that such opportunities for long-serving heads (and, indeed, other staff) should eventually become the norm, not the exception.

While “work-life balance” is probably an over-used and rather elusive concept, its importance comes through time and time again (and powerfully) in the comments of respondents to the HMC survey. Could it be that Tory leader David Cameron’s focus on GWB (“general well-being”) alongside GDP, as part of the new “compassionate Conservatism”, resonates particularly for school leaders?

Geoff Lucas is secretary of the Headmasters’ and Headmistresses’ Conference