The next time you think of getting on the phone and berating a head teacher - pause. It may make you feel better, but you will be contributing to a growing national crisis.

No one wants to be head of a school. Of primary schools that advertised for a new head at the beginning of this year, 26 per cent had to re-advertise.

Secondary schools in parts of the country find it even harder. Instead of headship being seen as the glorious pinnacle of a career, its joys and challenges making the long years of hard work all worth while, it is starting to be seen as tantamount to putting a loaded gun to your head.

At the National Association of Head Teachers (NAHT) conference, earlier this month, the ‘negative rhetoric’ spread by politicians and the inspectorate about teachers was blamed and particular attention was drawn to the heart breaking cycle whereby a new head or deputy with excellent credentials takes on a challenged school, and is given no time at all to bring about improvements before being ‘moved on’.

On the one hand, we want the best to go to where they are most needed. But why should they, if they know that within months, their school could be a ‘forced’ academy with a new governing body and new management?

Improvements, as anyone knows who stops and thinks about it, take time. It is not about fancy window dressing and one year’s results. It is not some heroic-style leader sweeping in, rubbishing the past and changing the uniform.

Educational enrichment needs a realistic time frame.

Those who want to carve out their own careers by destroying other people’s, take the high moral ground - ‘but the children only have one chance’. This is nonsense. Force feeding children, impressing parents and inspectors with your own bright new idea and bullying teachers, is not going to help children in any way that will last.

Successful schools and successful heads, like everything else, grow bit by bit.

The model successful head today is not one who would subscribe to a view that they personally could turn a school around. They would want to draw on the talent of their colleagues, try out ideas that were bedded in research, work closely with others whose input they would seek and value.

These are not quick fixes but they are what create sustainability.

If we want a pipe-line of idealistic, well-experienced and emotionally intelligent teachers to feed the service of headship, there needs to be a major change in how we think about flourishing schools.

* Sarah Evans, Principal, King Edward VI High School for Girls