Fifteen of the top 20 schools - measured by the proportion of entries awarded A and A* grades - are girls schools.
The top school by this measure is St Paul's Girls, a London day school (fees pounds 2,459), which retains a lead that it has held for four years, though with a slightly reduced proportion of top grades. Ninety-six per cent were at A or A*, ahead of Wycombe Abbey in High Wycombe, Buckinghamshire, a boarding school (fees pounds 4,750), which came second. All eight leading schools are girls-only. The top boys school is St Paul's in London, closely followed by Eton and Westminster.
Eton, which slipped back in last week's A-level league tables, seems to be holding its own at GCSE.
One reason for the dominance of girls schools is that girls outperform boys at GCSE. At A-level, boys are still gaining more top grades. Research suggests that single-sex education does not in itself give girls an academic advantage over those who are educated in co-educational schools.
The number of single-sex schools has declined sharply over the past 20 years but Elizabeth Diggory, head of St Paul's Girls, said there were strong arguments for their continued existence, because they offered choice. "You cannot possibly claim that all-girls schools are right for every girl but there is some evidence that some girls suffer in a mixed environment. For some they provide vital confidence during adolescence."
The figures for 600 independent schools that are members of the Independent Schools Council were released by the Independent Schools Information Service and compiled by Monckton Combe Computing Service.
Overall, more than half of all independent school entries achieved A and A* grades, up from 48.2 per cent last year. That was a bigger rise than for all schools, reflecting the selective-entry policies of many fee-paying schools. Nationally, 15.2 per cent of entries were awarded A and A*s compared with 14.7 per cent last year.
The difference between independents and the rest for the coveted A* grade was even greater - 19.7 per cent for the independents compared with 4.4 per cent overall. On average, independent school pupils took 9.2 subjects each.
Critics of GCSE say that the annual rise in the proportion of pupils getting top grades shows that the exam is getting easier.
But Miss Diggory said: "A century ago only a very small proportion of the population could read and write.
"The fact that the vast majority of people now can doesn't devalue reading and writing. I think that schools are focusing their teaching much more. We know more about the exam because the exam boards tell us more.
"There is a lot of good teaching and strong motivation among pupils."
She said the girls at St Paul's did well because they were "interesting, lively and inquiring" and were involved in many extra-curricular activities as well as schoolwork.Reuse content