Statistics from the Independent Schools Information Service show that 33.5 per cent of the public-school entries this year were awarded an A-grade - up nearly 2 percentage points from 31.7 per cent last year. This was twice the national average of 16.8 per cent.
The figures, based on a provisional list of results from 520 independent schools, raise serious questions for ministers if they are to meet their commitment to bridge the gap between the state and private sectors.
And they appear to confirm that state-school pupils are increasingly disadvantaged in the competition for places at the top universities.
ISIS says that nearly half of all the 1998 GCSEs taken by public- school pupils resulted in A* or A-grades. Provisional GCSE results from nearly 39,000 candidates from 608 schools revealed that 48.2 per cent of all entries were graded A* or A, compared with 45.2 cent last year. The national average was 14.7 per cent.
Independent-school candidates took an average of 9.2 subjects at GCSE while the average Universities and Colleges Admissions Service points score per candidate was 21.95 compared with 21.6 for 1997 candidates - a 1.6 per cent improvement.
There were a total of 106,427 subject entries (excluding general studies) from the 520 schools at A-level - 100,687 at A-level and 5,740 at AS-level.
More than a third (36.7 per cent) of the entries from the 201 candidates who took advanced GNVQs, received distinctions.
Meanwhile a survey of nearly 450 fee-paying boarding schools by the ISIS has revealed they are as confident or more confident about their future than a year ago.
It showed a 3 per cent increase in a feel-good factor among heads with 84 per cent now registering a belief in the future of boarding.
The survey disclosed that parents were continuing to take a keen interest and that boarding schools were investing heavily with 38 per cent planning major spending during the next year.