This is probably a state secret, but I will share it with you anyway.

Ofsted inspectors are not infallible. The Friday article, “Ofsted Overruled” (June 17), described how headteachers in two schools succeeded in “overturning” inspectors’ special measures judgments. It was slightly misleading, however, in representing the HMI visit as a “reinspection”.

That might seem to be the case, but schools that expect the HMI visit to be a second bite at the cherry are likely to be disappointed.

Inspectors do not put schools into categories for the sheer fun of it. The decision to put a school into special measures is a particularly grave one for inspectors, because they know it will mean their evidence will be carefully scrutinised and they will probably have to answer complaints from schools that are initially in denial. Although lead inspectors are usually paid a few hundred pounds extra for putting a school into special measures, this rarely compensates fully for the extra time and work involved, post-inspection, where a school has been “failed”.

Under the current and preceding frameworks, inspectors are required to ask themselves a cascade of questions. Is the school failing to provide an adequate standard of education, or is it likely to fail? If the answer to these questions is “no”, inspectors then have to ask if the school has serious weaknesses or is underachieving. Handbooks include prompts and descriptors which help inspectors to interpret their evidence to answer these questions. (Most staffrooms will have a copy of the handbook on the shelf.) The category of underachieving school is particularly misunderstood, by inspectors as much as by schools. Originally intended to identify “coasting schools” which seemed to be doing okay but where pupils were capable of doing better, it has sometimes been misused as a third tier down for a school with significant shortcomings but not quite serious weaknesses.

As soon as it looks as though placing the school in one of the categories might have to be considered, the lead inspector is expected to telephone Ofsted and talk to an HMI. At this stage inspectors probably shouldn’t be asking for advice as the best HMI would refuse to give it; they, after all, are not the ones in the school or with the evidence in front of them.

However, the conversation enables the HMI to quiz the lead inspector and help them reach their decision. It also means that Ofsted has a log of what is happening.

When inspectors decide that special measures are required, they are, in essence, making a recommendation to the chief inspector. The lead inspector will be expected to package together all of the inspection evidence and get it to HMI, along with an early draft report, by an agreed date, usually within a couple of weeks of the inspection. This is because, uniquely in the case of a recommendation that special measures are required, the inspectors’ findings are subject to HMI corroboration.

HMI will contact the headteacher and ask whether the school is content for this to be “paper corroboration” (via scrutiny of all the inspection evidence) or whether the school would prefer an HMI visit. Schools disputing the inspection team’s findings are most likely to ask for the visit. Although it will give the school a face-to-face opportunity to voice their view that the team have got things wrong, it will essentially be a visit to corroborate (or otherwise) the inspection findings, not to reinspect the school from scratch. HMI will go into the school, having read the draft report, to see whether they come across similar shortcomings to those noted by the team. In the overwhelming majority of cases, they will concur with the decision of the inspection team.

The examples cited in The TES were very much the exception to the rule.

Indeed, the concern that has been voiced by HMI in the past is that inspectors have been more likely to go too far the other way, being reluctant to make and communicate tough decisions. After all, we have probably all gossiped about schools - usually someone’s else’s! - which have “got away with” a satisfactory Ofsted report.

Selwyn Ward is a registered inspector who has led 60 primary and secondary inspections and taken part in around 200