The Funding Agency for Schools' latest value-for-money report claims that there is no correlation between the teaching costs per pupil and the percentage achieving five or more A* to C grades at GCSE.
Perhaps anticipating teacher ire, the report hastily adds: "This is not to say that levels of expenditure on teaching will never have any effect on performance. Significant increases and reductions in expenditure on teaching are both likely to have an impact, to some degree, on performance."
But an agency spokesman confirmed that within the range of data available for 616 GM secondary schools, it made no difference whether they spent pound;1,400 or more than pound;2,700 per pupil when it came to top-grade GCSE passes.
The statisticians who compiled the report also found there was no correlation between GCSE performance and school size.
Schools with sixth forms generally achieved better results for five top-grade GCSEs, but Years 12 and 13 made little difference in the figures for five A* to Gs or one or more A* to G passes.
The report found a strong correlation between GM admission policies and performance. Selective schools were top of the performance tables, with 95 per cent pass rates for five A* to C grades, with comprehensives achieving 47 per cent, and secondary moderns 30 per cent.
Ten supplementary reports look in more detail at the figures relating to particular groups of schools - for example, large secondaries with sixth forms. These are being distributed to complement the schools' own performance data and the Office for Standards in Education's performance and assessment reports.
The supplementary reports compare individual schools' anonymous data, and introduce three new ratios on key indicators. They are: net surplus or deficit as a proportion of total revenue income; educational costs as a proportion of total revenue income; and the ratio of current liabilities to current assets.
Copies of the reports are available from the FAS' value for money unit on 01904 661540.