For the first time this summer half of all A-levels at private schools scored the top grade, according to data released on Saturday.
The record results for the 476 members of the Independent Schools Council cap years of continuous improvement and will fuel concerns that A-levels are failing to help university admissions tutors and employers distinguish among the very best candidates.
According to the ISC’s report, 75 per cent of entries were grades A or B. Nationally, including results from state schools, 25.3 per cent of entries were awarded a grade A.
Jonathan Shephard, chief executive of the ISC, said the results reflected the ability and effort of the 31,347 pupils at the schools and the skills of their teachers.
Eton College came top of the league table for its exam performance this year when measured against the point system used by the Universities and Colleges Admissions Service. Boys at the boarding school near Windsor achieved an average of more than four As each.
Other well-known private schools at the top of the tables included Westminster School, Wycombe Abbey and North London Collegiate
One notable omission was Winchester College, the all-boys academic powerhouse which has become one of the leading critics of the current A-level system.
Earlier this summer Ralph Townsend, the school’s headmaster, wrote to parents telling them that the school would not provide results data to the ISC. He said the league tables drawn up by newspapers from the ISC information did not reflect the school’s true academic performance.
The school has also made clear its desire to abandon A-levels if trials next year of a new qualification, the Cambridge Pre-U, prove a success. The Pre-U, which will be available for teaching from next year, will involve studying three subjects over two years, with final exams and an extended essay.
Currently, A-levels are modular with exams taken in units during the course.
Dr Townsend told parents that over the past 25 years the “content and rigour” of A-levels had been reduced by the “aggressive programme of successive governments to increase access to universities”. “The academic content of science and language courses, in particular, has been progressively eroded.”
The government has announced measures to try to shore up support among private schools for A-levels as schools consider rival qualifications, including the International Baccalaureate.
They include new questions designed to “stretch” students and a new A* grade for the very best candidates.
Research released by the ISC on Saturday showed the independent sector continued to dominate maths, sciences and modern languages while pupils at maintained schools were more attracted to “softer” subjects such as psychology and media studies.
According to Cambridge Assessment, 70 per cent of state schools offered psychology in 2005, compared with 32 per cent of independent schools at A-level.
Media studies was offered by almost half of comprehensives but only 10 per cent of independent schools.
The private sector is also moving into non-European languages, with Mandarin offered by 43 per cent of independent schools and five per cent of comprehensives.