The reaction by Ofsted’s chief inspector Sir Michael Wilshaw (inset, right) to the criticisms of Professor Robert Coe is typical of the circular and arrogant thinking so often heard in schools when Ofsted comes to call - we say it is so and therefore it is so.

The current system that relies on observations of part lessons, a 25-minute chunk from which judgements are extrapolated about the quality of the whole meal, must surely lead to some inaccuracy. Short-notice, two-day inspections mean that inspectors have to arrive at a school with a hypothesis based on published achievement data. Does that colour the judgement of the 25 minutes seen of the first lesson of the day? Many schools find that their lesson observations are less favourable on the first morning.

The point is that, as Professor Coe notes, there is no evidence other than anecdotal to give us confidence in the system. Instead, we have to put up with a circular argument: if achievement isn’t good, then teaching can’t be good and nor can your leadership.

Ofsted-style lesson observation devalues the complexity of the craft of teaching and undermines the professionalism of teachers. Inspections are a blunt tool that need reforming. Evidence-based accountability would be a good place to start.

Stewart Goacher, Leicestershire.