Ofsted’s new curriculum-focused inspection framework means that schools' "outstanding" judgements are about to become even more out of date, Amanda Spielman has warned.
The chief inspector said today that some schools will now have top inspection ratings that are four frameworks out of date.
Schools given "outstanding" grades are exempt from routine inspection, and some have gone more than a decade without a visit from inspectors.
Background: Ofsted keeping four inspection grades
Need to know: Ofsted's new inspection framework
Today Ofsted launched the new framework that it will use to inspect schools from September – which will have an increased emphasis on curriculum and give less weight to exam results.
Ofsted wants the government to lift the inspection exemption on "outstanding" schools.
Ofsted inspection changes
Ms Spielman warned: “There are reports out there that relate to schools inspected not just under the current framework but going back three or four frameworks ago that really are in some ways quite significantly different, so, yes, the further it gets from the current framework the less comparable it is.”
Ofsted is proposing to keep the four inspection grades under the new framework, which comes into effect in September.
Schools rated as "outstanding" have been exempt from routine inspection since 2012 but inspectors can go in where concerns are raised about standards or safeguarding.
In a recent blog, a senior inspector warned that the "outstanding" grade had been devalued for some parents because inspectors are not able to routinely check on top-rated schools.
HMI Dan Lambert said that many parents, teachers, leaders and governors felt that "outstanding" schools being exempt from inspection was not in the school or pupils' best interest.
Ofsted also revealed last month that the majority of parents were unaware that "outstanding" schools are exempt from routine reinspection.
It was revealed last year that 1,620 schools had not been inspected for six years or more. This included almost 300 schools that had not been inspected for 10 years.
Schools standards minister Nick Gibb has asked Ofsted to inspect at least 10 per cent of "outstanding" schools.
He made this statement last year after pressure from the inspectorate to end the exemption on "outstanding" schools being routinely visited.