Figures released by the Department for Education yesterday show that nearly 43 per cent of girls gained five or more top A to C grades in last year's exams, against 34 per cent of boys.
At A and AS-level, by contrast, 12 per cent of boys scored the equivalent of three A grades or three Bs and a C, against 8 per cent of girls.
Education researchers and teachers have long disputed the reasons for that shift.
There is firm evidence that the increased use of course work to grade pupils in the GCSE exams led to a sharp improvement in girls' grades, suggesting that girls apply themselves more carefully to working during the course, while boys tend to fare better at the traditional set-piece exams.
Some argue that girls and boys develop at a different rate, while others suggest that sex stereotyping leads to girls performing better in arts and humanities subjects, while boys do better in science and maths.
The GCSE figures show that boys only do marginally better than girls at mathematics, are no better at science and that more girls enter exams in those subjects.
The most striking gaps in GCSE performance are in English - 56 per cent of girls gained top grades against 40 per cent of boys - and modern languages - half of girls entered gained top grades compared with one-third of the boys.
Although fewer girls attempt technology at GCSE, they are more likely to collect a high grade. About 140,000 boys took technology GCSE last year, compared to only 35,000 girls - the widest sex bias - but nearly half of the girls gained top grades, compared to one-third of the boys.
More girls take business studies GCSE and do better than boys by a similarly wide margin. They were also significantly more likely to gain top grades in geography, history, and religious studies.
At A-level, although boys were overall more likely to collect high grades, girls had better success rates in technology and physics, which are traditionally regarded as boys' subjects. Boys did better at history and French. More than twice as many 18- year-old girls take A-level English, while nearly twice as many boys take maths - but, as a proportion of entrants, girls gain slightly better grades overall in those two subjects.
DFE Statistical Bulletin No: 15/93 can be obtained from the department's Analytical Services Branch, Mowden Hall, Staindrop Road, Darlington, Co Durham DL3 9BG.
A survey released yesterday by the Association of County Councils and the Association of Metropolitan Authorities shows that 65 per cent of 16-year-olds are now choosing to stay on at school, up from 48 per cent four years ago.
The survey confirms government figures earlier this week, which show that 55 per cent of 17-year-olds are remaining in full-time education and 34 per cent of 18-year-olds.