Details of exactly what exams academies are entering pupils for will become publicly available within months, following ministers' decision to bring the state-funded independent schools under the Freedom of Information (FOI) Act.
It will give academies the same legal responsibilities to be open about information as conventional state-funded schools and other public bodies.
The news has been welcomed by critics who claim the Government's justification for its massive expansion of the sector is flawed because it is based on the notion that academy GCSE results are rising at twice the rate of mainstream state schools.
Last week, parliamentary questions revealed that in 2009 only 49 per cent of academies "GCSE" results were actually made up of academic GCSEs, compared with 73 per cent for other state schools.
The critics allege this is because academies are using "highly questionable, pseudo-vocational" courses to help them climb the league tables.
Others reject this and say academies are offering reputable vocational courses as an important way to educate and engage pupils, often from deprived backgrounds, helping to spur them on to academic achievement.
But until now it has been impossible to find exactly what courses all academies are entering pupils for because, unlike other state schools, they have not been covered by FOI laws.
Now ministers say that all schools converting to academy status this autumn will be immediately covered by the act, with existing academies added from January 2011.
The concession came in response to an amendment proposed to the Academies Bill by Lord Lucas, a Conservative peer who described the Government's decision as "very cheering news".
Anastasia de Waal, education director of the think-tank Civitas, said: "This is very positive but there is an outstanding issue - that the evidence base for academies still isn't there."
She said that if the Government wanted its academies policy to have credibility then it needed to collate and reveal their exam results now.
Civitas tried to find out academies' detailed results last year but found it impossible because the Government did not collect the information and they were not subject to FOI laws. The think-tank surveyed the heads of 118 academies and found that although 80 per cent saw exam results as an indicator of their school's progress, only 55 per cent thought they should be made publicly available broken down by subject.
The Government has so far failed to respond to further parliamentary questions from the Labour MP and historian Tristram Hunt asking for details of what qualifications each academy had entered pupils for.
Letters, pages 26-27.