Independent schools want the exams to be reformed

The Independent Schools Council found 46% in England and Wales had made the top grade, up from 43.4% last year.

The overall proportion of A-level entries which achieved an A grade this summer was 22.8%.

The ISC, which represents most large private schools, says the exams need to be reformed so universities can choose between high-quality candidates.

'Real difficulty'

ISC general secretary Jonathan Shephard said achievement was "astonishingly high" among the 30,880 pupils in its member schools.

He added: "Leading universities do experience real difficulty in identifying the very best candidates.

"With relatively minor reform, A-levels can be made to do the job."

The ISC supports the inclusion of more difficult questions, which ministers have promised to introduce.

Mr Shephard also backed the idea of adding A+ and A++ grades.

He said: "The alternative is a proliferation of individual university and departmental entrance tests, which will add to the pressures on candidates and schools."

In league tables of independent schools based on the ISC's A-level data, Westminster School in London came top for the second year in a row.