Granting academy freedoms to every school - a cornerstone of the government's education reform agenda - is not a "panacea for school improvement", a panel of high-profile experts has warned.
The conclusions of a major report, published yesterday, came just days after the publication of the coalition's midterm review, which pledged to step up the academies programme.
The independent Academies Commission, led by former Ofsted chief inspector Christine Gilbert, has questioned the expansion of the programme in the absence of a coherent plan. While praising its "ambition", the report said the programme has focused too much on increasing the number of state independent schools and not enough on school improvement.
Ms Gilbert was joined on the commission by Chris Husbands, director of the University of London's Institute of Education, and Brett Wigdortz, chief executive of Teach First. They have spent the past seven months examining the academy landscape.
Since 2010, the Department for Education has overseen the conversion - both voluntary and enforced - of more than 2,600 schools to academy status.
But the commission, working on behalf of the RSA and the Pearson Think Tank, has called for clearer proposals, adding that a "determined focus on the detailed implementation of the academies programme" is necessary if it is to be effective.
Ms Gilbert told TES that the response to the academies policy had taken the government by surprise and that it was time for a more careful approach. "The focus has been on increasing numbers and if the focus is to be on increasing quality, we think there needs to be much more care taken about building in things that will support improvement," she said.
Too many schools that had converted since 2010 had become stand-alone academies, Ms Gilbert added, and were not fulfilling their commitment to support other schools to improve.
The commission's report also highlights concerns around academy sponsorship, calling for an end to the "beauty parade" of selecting sponsors, and recommending funding agreements be cut from seven to five years in length.
The proposal follows a National Audit Office report released at the end of last year, which found that almost half of all sponsored academies were judged to be "inadequate" or "satisfactory".
Russell Hobby, general secretary of heads' union the NAHT, agreed with the commission's report, adding that the academy model was not a "silver bullet".
"They (the government) have gone for quantity over quality because they want to talk about how many they have converted," he said. "But they have not asked: is this the right strategy for every school? Sometimes it is, sometimes it isn't, but it cannot be treated as a silver bullet."
Ros McMullen, principal of the David Young Community Academy in Leeds, said the first wave of academies brought in under the Labour administration improved their performance, but said academy conversion was no guarantee of success.
"I am a firm believer in state independence," she said. "Academies are about innovation and entrepreneurship... But you don't get the same results if you just change the name of the school."
A spokesman for the DfE said: "GCSE results in sponsored secondary academies improved at more than twice the rate of maintained schools' results. And we have expanded the sponsored academy programme so that thousands of primary school pupils will now also get the first-class education they deserve."
Recommendations of the Academies Commission report:
The government should link the academies programme more closely to school improvement.
Local and central government should encourage the federation of primary schools without an immediate emphasis on academy status.
The Department for Education should "pump-prime" the establishment of a Royal College of Teaching.
The education secretary should identify an organisation to provide an independent admissions appeals service.
Local authorities should give up responsibility for school improvement and become champions for local children.
Local authorities should have a say in terminating academy funding agreements where provision is failing.
The Office of the Schools Commissioner should produce an annual report on academy chains' comparative performance.