Although the differences are marginal - in some cases only 1 per cent - the findings will be seized upon by ministers keen to promote the grant-maintainedsector as one of excellence.
Pauline Latham, chairman of the Grant-Maintained Schools Advisory Committee, said: "If Labour wins the election, it should look very hard at what we are doing to raise standards IThis experiment is not an experiment any more. "
But Martin Rogers of Local Schools Information, which opposes opting out, said the statistics were based on crude data that failed to take into account socio-economic factors such as free school meals. "It is outrageous and unprofessional for OFSTED not to put these figures into context. It is giving half a story to an audience which will distort it."
The statistics were provided by Mike Tomlinson, director of inspection at OFSTED to a conference for people working in GM schools. Analysis of key stage 1 results (for pupils aged seven) in English, maths and science, reveals that GM schools have more children reaching level two and above.
According to OFSTED, only 4 per cent of GM secondaries gave less than satisfactory value for money compared with 11 per cent of LEA equivalents. And it rated 40 per cent of LEA secondaries as providing less than satisfactory cost effectiveness, compared with 33 per cent of GM secondaries.
On the quality of teaching, it graded 48 per cent of lessons in GM secondaries and 43 per cent of lessons in opted-out primaries at levels one or two. Comparative figures for the LEA sector were 47 per cent and 41 per cent.
It recorded the same figures for the quality of learning in GM schools. The respective figures for LEA schools were 45 per cent and 42 per cent.
OFSTED said the statistics had to be treated cautiously but Mr Tomlinson told the GM heads: "What you are achieving with your pupils is high overall and is consistent with national expectations, given their ability."