A study of the reliability of Ofsted inspections has provided "a welcome positive view of inspector consistency", the chief inspector has said.
Amanda Spielman, who took up her post at Ofsted at the start of this year, added that these findings should provide reassurance about the process of inspection.
Ms Spielman's comments followed the publication this morning of a report into the reliability of Ofsted's short inspections. The report concluded that these inspections are more than 90 per cent reliable.
The study involved sending two inspectors to visit 24 primary schools that had previously been rated “good” by Ofsted. In 22 out of these 24 inspections, the inspectors independently reached the same conclusions about the schools.
This is equivalent to 92 per cent consistency in these inspections.
Inspectors reached the same conclusions in these cases regardless of whether they had conducted different inspection activities, or the same activities in a different order.
The study, published today by Ofsted, states: “Variation in inspection approaches did not commonly lead to disagreement at the end of the inspection.”
Commenting on the study, Ms Spielman said: “The study provides a welcome positive view of inspector consistency... These findings should provide some reassurance that the purpose of the short-inspection model is being met, and that inspectors made consistent judgements."
She added that, as with school exams, there is likely to be little tolerance of variation – however small – in inspection judgements. But she said: "We would not want to oversimplify inspection in the pursuit of consistency.
"A tick-box approach, for instance, might lead to improved reliability, but would be a mechanistic approach to inspection that would almost certainly undermine its validity."
Robert Coe, the Durham University professor who had previously called for an academic investigation into the reliability of Ofsted inspections, told TES prior to the report’s publication that 90 per cent reliability was a good outcome.
“The reality is that this is a subjective judgement process – you’re not going to have 100 per cent agreement,” he said. “The reality is that we’re going to have to live with some misclassification or subjectivity.”
The report also suggests that training of inspectors has had a considerable impact on the consistency of inspection judgements. It said that this training led “to greater adherence to the inspection framework and therefore greater reliability”.
Good schools are given a short inspection by Ofsted, to determine whether or not the school is still continuing to provide a good standard of education. If the school remains "good", then this is confirmed at the end of the short inspection. If its standards have dropped or improved, then the inspection is converted into a larger, full inspection.