The pass rate for top grades achieved by A-level entrants from fee-paying schools has fallen, figures show.
The number of A-level entries from private school pupils awarded at least an A grade dropped to 49.3% this year, down 1.2 percentage points on last year.
This was still almost double the national average of 25.9%.
A fifth of entries were awarded the top grade of A*, according to the Independent Schools Council (ISC).
One in 14 candidates got three A* grades - an outcome described by ISC chairman Barnaby Lenon as "remarkable".
A high proportion of the results will have been in traditional subjects such as maths, foreign languages and the sciences. "Many top university departments offering these subjects are dependent on independent school pupils for the quality of applicants they seek," Mr Lenon said.
"Independent schools continue to be strong across the country, with many schools in the North achieving the top grades, when national figures show that schools in the North are performing significantly worse than those in the South East," he added.
The ISC figures show the results of 484 independent schools and combine a range of qualifications including A-levels, the International Baccalaureate (IB), Btecs, the Extended Project Qualification and the Cambridge Pre-U examination.
This year's rate of 49.3% for entrants receiving grades A* or A represents a fall of 2.1 percentage points on 2012.
The drop mirrors a similar though smaller drop in the national figure, which was 26.6% in 2012 and is now 25.9%.
ISC general secretary Julie Robinson said: "These results reflect the hard work and dedication of pupils and the exceptional level of teaching and support in independent schools.
"ISC includes a wide range of schools, both selective and non-selective, and all provide young people with a bespoke education. Alongside a strong set of A-level results, schools continue to value their freedom to choose alternative qualifications, including the IB, Pre-U and the Extended Project Qualification."
The figures also show a rise in the number of pupils from private schools taking qualifications other than A-levels:
:: There was an 11% increase in students taking the Extended Project Qualification (EPQ). A total of 3,203 pupils (8.6% of those included in the ISC survey) took the EPQ this year
:: International Baccalaureate (IB) students rose by 7%, with 2,045 pupils (5.5% of the total survey)
:: The number of pupils sitting the Pre-U examination rose by 10%, with 1,516 students (4.1%) taking at least one Pre-U
:: Btec students rose by 31%, with 696 pupils (1.9%) taking at least one
Separate analysis by the Daily Telegraph suggests pupils at state schools are performing better in exam league tables than fee-paying students.
A comparison of Department for Education figures found that candidates from England's 500 leading state schools outrank the top 500 private schools when measured on points scored per pupil.