Inspectors' judgments on failing schools could be seriously flawed in as many as one in six cases.
Eighteen per cent of the primary schools failed since last summer are actually making good progress in English and maths when their results are analysed using the "benchmark" methods devised by the Qualifications and Curriculum Authority.
The new analysis by The TES is based on the latest 100 schools to be failed by the Office for Standards in Education.
The figures suggest that when the poverty of a school's pupils is taken into account - using the QCA formula - many primary "failures" are performing much better than OFSTED indicates.
Of 66 primaries producing key stage 2 results, 12 scored above average in both maths and English, given the backgrounds of their pupils. A further five were scoring above average in one of these key subjects and below average (but above the bottom 25 per cent) in the second.
The disparity points up the conflict between OFSTED judgments and national curriculum test scores.
The match between OFSTED and QCA figures is much better for the failing secondary schools where only two of 12 turned in better-than-average GCSEs.
Although comparatively crude, the QCA's benchmarking analysis is meant to provide a basis for comparing like with like. It works by grouping schools according to poverty levels (judged by the number of pupils entitled to free school meals) and then listing the national average test scores and GCSE results for each group.
So, at Archibald school in Middlesbrough, for example, 49 per cent of the pupils are eligible for free meals - more than double the national average of 21 per cent. The proportions of 11-year-olds hitting the government target of level 4 for maths and English respectively are 66 and 58 per cent.
According to the QCA, these results place Archibald in the top 50 per cent for English and the top 25 per cent for maths among schools in its category.
Both the school and the local authority are appealing against OFSTED's judgment. Similarly at St Patrick's primary in Manchester, 77 per cent of pupils are eligible for free dinners. Again the results - 50 per cent in English and 46 per cent in maths - put the school in the top 50 per cent of performers. This is despite the fact that results in both subjects were condemned by inspectors as "below the national average" and "unsatisfactory".
However, many of the primaries failed by OFSTED did have very poor results. Thirty seven per cent of these schools scored in the bottom 25 per cent for both English and maths.
OFSTED said this week that a school can be failing across a range of "key indicators" - inadequate management or poor pupil behaviour for example.
"Inspection goes beyond a measurement of outputs," said a spokesman. "It gives a more comprehensive picture of what is going on in a school community."
He said that OFSTED has been investigating the disparity between inspection judgments and test results, and promises a report in the near future.
THE CONTROVERSIAL 17
Oakfield county junior, Dartford
Prince Rock primary, Plymouth
Central Park primary, Newham
Hatherden CE primary, Andover
Burnt Tree j and i, Sandwell
Lewisham Bridge primary, London
Belle Vale primary, Liverpool
Parkinson Lane primary, Calderdale
Sir Theodore Pritchett primary, Birmingham
St Teresa's junior, Liverpool
Marston Green junior, Solihull
Archibald primary, Middlesbrough
St Patrick's RC primary, Manchester
Oxley junior, Wolverhampton
Saviour CE primary Manchester
Rathbone JMI, Liverpool
Llangrove primary, Ross on Wye
Leader, page 14
Additional reporting by Elaine Hines and Francis Gilbert