Ofsted grades are misleading parents and are wrong in up to half of cases, a former Government adviser has said.The lack of consistency is so severe that grades should be scrapped altogether, according to new report by Tom Richmond who is now director of EDSK, a think-tank specialising in education and skills. He cited research which demonstrates that thousands of schools could have been given the wrong rating over the years.Two international studies from 2012 and 2013 showed that different inspectors can reach different judgments about the same school in as many as 50 per cent of cases.Ofsted currently uses a four-point grading scale: outstanding, good, requires improvement and inadequate. Rather than trying to judge the overall performance of the school, Ofsted should concentrate of inspecting pupil behaviour, the quality of a school’s curriculum, careers advice and extra-curricular activities, the report said.Mr Richmond, who was an adviser to former Education Secretaries Michael Gove and Nicky Morgan, said: “We know that many parents use Ofsted grades when choosing a school for their child.”But these same parents have never been told these grades could be very misleading in terms of how well a school is performing.”Instead, we should focus on giving parents simple, accessible information to help them decide if a school is right for their child rather than Ofsted trying to come up with all the answers themselves.”Ofsted has published its proposals for a new inspection framework, which will come into force this September.Under the new framework, schools will be marked down if pupils misbehave and are discourteous to each other. In the new framework, the “personal development” category will examine what schools do to build young people’s resilience and confidence. This could include running a debating society, sports teams, drama clubs of cadet forces. Inspections in England will no longer focus on exam results and grades, and instead will concentrate on whether pupils are being taught a broad curriculum, the framework says. An Ofsted spokesperson said: “We are open to serious debate about how we inspect, as shown through our recent consultation on a new inspection approach. We will be publishing the outcome soon.” Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.