It was as if they had written the report before the inspection and then just looked for the evidence to support it. It’s all about the data, isn’t it?

It may have been slow to arrive, but glasnost officially became part of the Ofsted culture around five years ago. Lead inspectors have always been expected to spend time before the inspection going through the initial evidence available to them and drawing up a pre-inspection commentary as a briefing note for the rest of their team. (This will continue from September, but from then on it will be rather shorter and called a pre-inspection briefing.) The big difference is that whereas this used to be a secret document, seen only by the inspectors, there is now an expectation that the briefing note is shared with the headteacher, who then has an opportunity to add comments or to point out, in advance of the inspection, where they think inspectors have got the wrong end of the stick.

The pre-inspection briefing notes are intended to help focus the inspection, so that inspectors can direct their attention to what and why particular subjects or aspects of the school are especially strong or notably weaker than others.

From September, the notes will point inspectors in the right direction when judging the accuracy and incisiveness of the school’s self-evaluation. In doing this, inspectors are expected to form initial hypotheses, drawing on the data from the school’s Performance and Assessment report (Panda) and on the headteacher’s commentary on results. If, for example, the headteacher glosses over seeming underperformance suggested by the Panda, that may suggest management weaknesses that need to be followed up.

That should not mean, however, that inspectors have made their minds up about the school before they arrive. Sometimes initial hypotheses are confirmed, but often they are quickly rebutted. The fact that they are shared openly in advance of the inspection should be seen by headteachers as an opportunity to question the lead inspector at the start, not dismissed with despair as evidence that Ofsted are going into the school with a closed mind.

However, there is a potential downside to inspectors’ openness. If there is something in the pre-inspection briefing that the headteacher disagrees with, there is no point behaving like a rabbit in Ofsted’s headlights.

Since heads have the chance to raise concerns at the start of the inspection, they effectively bar themselves from complaining after the inspection about anything in the briefing that they failed to mention. When your pre-inspection briefing arrives, you had better speak now or forever hold your peace!

The woeful cry that “it’s all about the data” is understandable, but wrong.

Of course, the Panda data, showing how well the school’s Sats, GCSE or A-level results compare with others is important. The similar schools comparisons, which from key stage 2 up are based on pupils’ prior attainment rather than the less reliable indicator of eligibility for free school meals, give a valuable clue as to pupils’ achievement and the progress they have made over their time in school. They can suggest where there may be gender differences in performance and how well pupils of different abilities are doing.

In next term’s new-style Pandas, there will be evidence of differences in performance by pupils from different ethnic backgrounds. The data may, however, only tell part of the story or there may be all sorts of reasons why it may be terribly misleading. If we could rely simply on the data, Ofsted wouldn’t need to bother with inspections at all - schools with As in the current Pandas would be classified as very good schools and all those with Es would automatically be put in special measures.

In the current Pandas, comparisons between schools are made according to which benchmark band the school falls into. Inaccuracies can occur because the bands are very broad, so that, for a school on the cusp, there can frequently be a difference of as many as three grades depending on which side of the band the school falls into.

This absurdity will change with the new Pandas next term, but there will be fresh opportunities for error among the unwary, such as where graphically huge differences in ethnic performance refer to tiny numbers of pupils.

From next term, heads need to be alert to the fact that Ofsted will expect inspectors to be looking not so much at what the data is saying as what the school thinks the data is telling them - and what they are doing in response.

Selwyn Ward is a registered inspector who has led 60 primary and secondary inspections. He is one of a small number who has been involved in Ofsted’s pilot inspections before the new system is introduced in September.Patricia Denison is unwell