A study by the National Foundation for Educational Research found that specialist schools do slightly better than average at key stage 3 and GCSE. But non-specialist schools achieve lower GCSE scores when there are specialist schools in their area.

Language colleges do the best at GCSE, followed by technology colleges. But not all specialist schools performance is above average in all subjects. Pupils at sports colleges did not get significantly different results from those at non-specialist schools. And arts colleges achieved below average results for maths and science at KS3 and GCSE.

Even where performance is better, this may be partly the result of extra money or pupil intake rather than the specialism, the report suggests.

The researchers, who took into account pupils’ previous attainment, also studied religious schools. They found that Jewish schools got the best results and church schools performed consistently well in English but often underperformed in maths and science. They suggest that one reason for the higher performance of both faith and specialist schools is that they encourage high-ability pupils to take more GCSEs.

Sandie Schagen, who led the research team, said: “This confirms that specialist schools do have a very slight edge in terms of value-added performance but some of the claims made for them are clearly exaggerated.”