A charity campaigning for more free schools has raised "doubts" over the accuracy of Ofsted's judgements after analysis showed that a third of primaries given top ratings failed to meet the national average for key stage 2 attainment.
The study by the New Schools Network (NSN) claims that thousands of good and outstanding schools are “failing to teach the three Rs”.
The analysis came as ministers claimed that “enemies of academies” were “scaring and intimidating” parents who were supportive of their policies as they launched a consultation into new powers to intervene in underperforming schools.
The NUT teaching union said there had been a "series of pro-academy propaganda pieces" as the Education and Adoption Bill made its way through Parliament. The bill has drawn criticism from groups including the Catholic Church.
"The NUT is not uncritical of Ofsted," the NUT's deputy general secretary Kevin Courtney said. "However, it is an independent inspectorate, accountable to Parliament. Its inspectors judge schools, taking into account a range of evidence. It is better able to judge the quality of education provided by a school than the New Schools Network which, as its press release demonstrates, does not appear to understand the meaning of an average and recognise that some schools will be above and below average."
The NSN research claims that one in three schools (33.2 per cent) graded good or outstanding by Ofsted is falling short of average attainment – a total of 3,802 schools.
Overall, four out of five children (80 per cent) reach level 4 by the end of primary school – this is seen as the minimum needed for children to go on and successfully secure five GCSEs at A*- C. Of those who pupils do not attain level 4, just 6 per cent go on to achieve five good GCSEs.
Nick Timothy, director of NSN, said parents would be “shocked” that primary schools judged good or outstanding were failing to equip enough of their pupils with the basics.
"Free schools and academies are already more accountable than maintained schools,” he said. “They are accountable to the Education Funding Agency for their finances, to regional schools commissioners for their performance, and they're accountable to central government which can, in extremis, close them down.
"But this research shows that more needs to be done to improve accountability in the system as a whole.”
Elsewhere, Nicky Morgan said academies were being stalled by “campaigners” who deployed “underhand tactics, spread malicious rumours and intimidate parents”.
The education secretary announced plans to consult on tougher new measures contained in the Education and Adoption Bill, which would allow the government to intervene in schools deemed to be either “failing” or “coasting”.
“Our new measures will allow teachers to get on with the job of improving failing schools and deliver on our commitment to extend opportunity and deliver real social justice,” she said.
Ofsted responded to the research, calling it "fatally flawed" because it was based on the premise that a school could only be found "good" if its test results were above average every year.
A spokesperson said: "Under such a system around half the schools in the country would always be less than good, no matter who is running the schools and however much standards improve.
They added: “Our inspections do not just look at test results and progress levels. Our judgements also take account of the context of the school, and factors such as culture and behaviour, and whether children are safe and benefiting from a broad and balanced curriculum."