English schools have registered the biggest improvement in their GCSE results for 10 years, a TES survey has revealed.
The proportion of pupils gaining five or more passes at grade C or better has increased by 2.5 percentage points, from 51.6 to 54.1 per cent, returns from 89 of the country's 150 authorities reveal.
The figures, which are due to be officially announced next month, will enable the Government to achieve one of its key targets: to improve the GCSE score by two points a year. They come amid increasing evidence of the success of schools' investment in revision classes, extra coursework help and targeting borderline pupils.
One school, Sacred Heart RC comprehensive in Southwark, south London, told The TES how it had improved its score from 56 to 73 per cent this year, partly by giving teachers a mark according to their pupils' exam performance.
The survey which covered 1,659 secondary schools in 89 authorities, revealed the proportion of pupils gaining five or more passes at A* to C rose from 47.7 per cent to 50.1 per cent. If this achievement is replicated nationally, the percentage will increase overall from 51.6 per cent to 54.1 per cent.
However, there is some scepticism about the effect on the figures of a set of vocational qualifications - the GNVQ - which are deemed by the Government to count as four top GCSEs.
The focus on GNVQs comes because of a disparity between the survey's results and statistics released last month, which showed the numbers of top grades awarded, but no analysis of how this translates into individual pupils' results. They revealed an increase of only 0.2 percentage points in the top GCSE grades.
The number of entries for the GNVQ is rising much more rapidly than the number for GCSE and GNVQ combined.
The total number of exams taken rose by only 1.3 per cent this year. By contrast, the numbers entered for the full intermediate GNVQ, worth four top GCSEs, rose by 40 per cent, from 66,230 to 94,017. And the numbers passing rose by 22,000, at a stroke giving up to 3 per cent of those entered for GCSEs four passes at C or better.
Some heads are critical of the incorporation of GNVQ results into GCSE figures, which form the basis of the league tables, but most the authorities surveyed combined the two. Lawrence Montagu, head of St Peter's school, Gloucester, accused ministers of "misinformation". League tables should separate the two qualifications, he said.
However, Andy Schofield, head of Varndean school in Brighton, which has designed GNVQ information technology courses for sale to other schools, said: "These are good qualifications, which are proving popular. I think we should recognise that as a good thing."
St Luke's CofE school in Southsea, Portsmouth, which improved its score from 11 to 26 per cent of top grades, entered 51 of 164 pupils for GNVQ, with most passing. Head Krysia Butwilowska said other measures also contributed to its success, such as allowing pupils to concentrate on their strongest subjects, and running weekly tutorials for underachieving pupils.
The Qualifications and Curriculum Authority said that the National Council for Vocational Qualifications which developed the exam in the early 90s had come up with the four-GCSE equivalence formula. There were no plans to review it.
A Department for Education and Skills spokeswoman said: "GNVQs are not an 'easy' option."