In the latest table of "prices" for a three-A-level package in the various types of institution, GM schools have fallen to second place in the cost league after sixth-form colleges.
In an earlier set of figures leaked to The TES last month, opted-out schools topped the table for public funding for A-levels, followed by sixth-form colleges, local authority-run schools and, finally, further education colleges. That placing will have proved embarrassing for ministers, who have always proclaimed that their flagship GM school are highly cost-effective.
The first set of comparisons, published by the Department for Education and Employment last December, put GM schools in second place.
The latest figures are published in a consultation document on the funding of education and training for 16 to 19-year-olds published by the Government this week.
The third revision of the figures opens up the Government to further criticism from opposition parties and from colleges, which insist they are far more cost-effective than schools.
Ministers, who say the changes have arisen as new factors are taken into account in the calculations, will face accusations of adjusting their figures to suit political purposes.
Stressing the need for constructive dialogue, Education and Employment Minister James Paice said the consultation document would "help us to identify the funding mechanisms best suited to improving standards, encouraging fair competition between providers, securing better value for money and promoting greater choice and diversity". Comments must be sent to the DFEE by October 4.
The study compares the public cost of full-time tuition for three A-levels in schools and FE colleges, advanced GNVQs in FE colleges and NVQ3s in Youth Training.
It suggests that sixth-form colleges, at an average cost per student of Pounds 6,530, are more expensive than grant-maintained sixth forms (Pounds 6,445), LEA school sixth forms (Pounds 6,385) and general FE colleges (Pounds 6,180). Advanced GNVQs at FE colleges cost Pounds 7,675 per student on average, while an NVQ level 3 obtained via a TEC training provider cost Pounds 4,920.
The June figures, indicating that GM schools were the most costly, were described at the time as a "political own goal" by the Labour party. The DFEE says that there has been a marginal narrowing of the different costs in the refined analysis.