Three high profile multi academy trust chief executives have backed a report calling on Ofsted to change its new inspections so that schools are not penalised for running three year GCSE courses.
Sir Dan Moynihan, Martyn Oliver and Dame Rachel de Souza have said the watchdog needs to change its inspection framework to maintain its credibility.
The respective leaders of the Harris Federation, Outwood Grange Academies Trust and the Inspiration Trust have welcomed a report by the Policy Exchange think tank which accused Ofsted of having a "de facto preference" for schools to run key stage three over three years rather than two.
The report found that schools running a longer key stage three were more than twice as likely to be judged to be good by the inspectorate than those who started GCSE teaching in year nine.
And it called on the watchdog to change its inspection framework handbook so this was no longer the case.
Ofsted has said that it does not have a preferred length of key stage three.
However MAT leaders have claimed that Ofsted's new inspection handbook is putting inspection teams in an impossible position.
In a joint statement Sir Dan, Mr Oliver and Dame Rachel said: "We welcome this report, which is emphatic that Ofsted needs to take action to resolve the concerns that we and a wide range of others in the education sector share about the new framework.
"In particular, we believe that the framework disadvantages poorer pupils. The report recommends that Ofsted should delete the element of its framework that penalises schools with a two-year Key Stage three, and make wider modifications to be consistent with education statute and DfE guidance.
“Ofsted has said it has no preference about the length of the key stages, but the content of its new framework puts inspectors in an impossible position.
"We support a robust and rigorous inspection regime, and to maintain the legitimacy and credibility of its new framework the inspectorate now needs to match its framework to its rhetoric by implementing the recommendations of this report."
The Policy Exchange report follows the same MAT leaders speaking out over Ofsted's new inspection which Sir Dan has described as a "middle-class framework for middle-class kids”.
They raised concerns that schools are being marked down for running GCSEs over three years rather than two.
The Policy Exchange report calls for the watchdog to delete a line from its framework which says: “If a school has shortened key stage three, inspectors will look to see that the school has made provision to ensure that pupils still have the opportunity to study a broad range of subjects, commensurate with the national curriculum, in years 7 to 9.”
Asked to respond Ofsted repeated its comments on the Policy Exchange report: "We welcome its support for our new inspection framework and its backing for our strong stance against schools that game the system.
"We’ll continue to celebrate excellence in all types of school and to recognise academies and faith schools for exercising their freedoms in the best interests of their pupils. We’ll also continue to listen carefully to feedback on our work.”