Eight months before former education secretary Charles Clarke announced plans for 200 academies, ministers were told of doubts about the pound;5 billion scheme's ability to introduce more innovative teaching.
In a report commissioned by the Government, consultants PricewaterhouseCoopers also said academies could lead to a two-tier system based on social class and thwart the Government's policy of collaboration.
Ministers chose not to publish the 264-page document, the first of five planned annual reports evaluating academies, the expansion of which was announced last year.
The PWC report was given to ministers in November 2003 and obtained by The TES under the Freedom of Information Act. It suggests that academies will not necessarily lead to the teaching innovations that ministers have said are among their main aims.
The Department for Education and Skills said it did not publish the report because only a small number of academies were open when it was compiled.
In fact, the report makes no attempt to evaluate academies, but examines research into similar schemes. It cites introducing innovation to "increase choice and diversity" as an "ultimate" objective of the academies programme.
The authors identify US charter schools as a "close parallel" and note their innovative use of technology but say that, despite their greater autonomy, innovations in teaching and learning have been "modest". "When given greater autonomy and flexibility, some schools return to 'traditional' values and implement a curriculum with a strong emphasis on 'back to basics'," the report says.
PWC, which worked with York university on the report, says it is unclear whether academies will assist collaboration on recruitment or act as a constraint by increasing competition.
The report describes academies as the latest manifestation of an attempt to create a "quasi-market" in UK state education, which it says could have a detrimental impact and help develop a two-tier system, dividing pupils by social class. "Some studies have suggested that middle-class families tend to be more proactive in seeking what they consider to be the best school for their children, and they can use their 'cultural capital' to secure school places," it says. "Such concerns have already been expressed in relation to academies."
The report says the evidence on the net effect of such markets is finely balanced. One study found nearly half of school district (US education authority) leaders thought their budget had been reduced because of charter schools.
On the plus side, PWC says the study found charter schools had made the districts and other non-charter schools "more customer services-orientated". Generally, though, the report says competing in the marketplace can use up teachers' and heads' time on non-teaching activities associated with marketing the school.
It also raises the question of whether the DfES's direct role in overseeing academies is sustainable in the long term.
Mary Bousted, the Association of Teachers and Lecturers' general secretary, said: "This report demonstrates even more that if there is a directive from No 10 then evidence-based policy goes out of the window."