It appears to be accepted wisdom that you are about to carry out a Cabinet reshuffle. Can I enter a last-minute plea to you not to do so - at least not in education? Mr Balls may be a brilliant secretary of state in waiting for business, but he has got a lot of unfinished business at education and it would be crazy to move him at this particular juncture.

In 1997, Tony Blair gave every sign that he would keep ministers in post for a long period. With David Blunkett spending the whole four-year term of the first Parliament at education, he seemed to be keeping his resolution rather better than some of us manage each new year. Mr Blunkett remains the second-longest serving secretary of state after Keith Joseph.

Then “events, dear boy, events”, as Harold Macmillan used to say, took over: Estelle Morris resigned after 17 months; Charles Clarke was moved after 26 months as he was considered the best person to take over when Mr Blunkett left the Home Office under a cloud; Ruth Kelly never really fitted in and was moved after 18 months; Alan Johnson stayed only 13 months before yet another reshuffle moved him to health; and we have had Mr Balls for nearly two years. That’s six secretaries of state. Average term of office since Mr Blunkett: 19 months.

There have been seven schools ministers during the same period: Stephen Byers (14 months), Estelle Morris (nearly three years), Stephen Timms (12 months), David Miliband (31 months), Stephen Twigg (six months), Jacqui Smith (12 months) and Jim Knight (three years). Average term of office: 20 months.

Each secretary of state comes in with a shiny policy programme and, given that they can only expect a brief sojourn at education, they want it implemented in a hurry, while schools and colleges are still implementing the hastily legislated ideas from the last two secretaries of state. The result is that we have too many policies, too rapidly introduced and with no time to be properly evaluated before we have to move on to the next idea. That is not, I venture to suggest, good government.

With a year at most before a general election, it’s not a good time to take on a department as big as children, schools and families, with a huge and complex agenda that only a brain the size of a small planet could be expected to understand fully in that time. Added to which, an education bill is nearing the end of its flimsy consideration in Parliament, spawning numerous regulations and statutory and non-statutory guidance papers for each of its many measures. Meanwhile, a white paper is destined to appear in mid-June with a whole new set of proposals, leading no doubt to a bill rushed through in the autumn during a truncated and fevered pre-election parliamentary session. This white paper will, we know, contain some of Ed Balls’s “big ideas”, such as the report card, planned to be a more rounded system of school accountability than the existing league tables of examination results.

A new secretary of state would be unlikely to take on the Balls programme fully, so we will have a rush for a new version of the white paper before the summer recess, and legislation cobbled together for the Queen’s Speech in the autumn. Not good government, I am sure you will agree.

Schools’ policy has been inconsistent, sometimes even contradictory, and the frequent changes of minister have added to this incoherence. After 12 years of a Labour government, huge investment in education, greatly improved results and now the prospect of better co-ordinated children’s services to frontline institutions such as schools, you need to build on success, not rebuild in the image of a new broom. So you would be well advised to stick with the present one.

John Dunford, General Secretary, Association of School and College Leaders.