FAILING schools are up to 12 times less likely to improve if they are forced to become academies, sensational new figures showed yesterday.

As the government prepares to push through legislation which will force every school rated “inadequate” to move outside local authority control, campaigners have raised fears of a cover-up that kept the data secret until now.

Teaching unions urged ministers to scrap the proposals for involuntary academisation last night.

The figures, published in response to a Freedom of Information (FoI) request lodged by education blogger Henry Stewart, is the first record of the effect of academisation on underperforming schools.

It shows that 27 per cent of secondary schools rated “inadequate” and then converted to sponsored academies remained below par compared to just 7 per cent of those which stayed in council hands.

For primary schools the gulf was even wider, with 8 per cent of converted underperforming schools remaining as such, compared with 0.6 per cent of those that kept their status.

National Union of Teachers deputy general secretary Kevin Courtney blasted: “Parents will rightly question the motives of a Secretary of State for Education who appears hell-bent on pursuing a policy agenda that isn’t evidence-based and clearly not in the interests of children and young people.

“One can only assume that [Nicky Morgan’s] determination to hand over England’s schools to unaccountable academy sponsors, with the valuable land and buildings that goes with them, is driven by a commitment to privatise our schools at all costs.”

ATL general secretary Mary Bousted echoed Mr Courtney’s criticism, saying “academy conversion is no panacea for failing or coasting schools.”

“The House of Lords should take note of this evidence and reject the Education and Adoption Bill’s provisions to turn ‘coasting’ schools into academies,” she said.

Mr Stewart, who is active with the Local Schools Network, questioned why the Department for Education had published an analysis of the changes in Ofsted ratings for voluntary converter schools but not an equivalent for sponsored academies.

In response to his FoI request he was told that four meetings were held to discuss this report but that no minutes were made of those meetings.

“Did the DfE cover up these figures?” he asks in a blog post.