Teenagers scored a record number of top grades in their A-levels this summer, as the national pass rate rose for the 25th year in a row.
For the first time, the proportion of exams awarded A-grades reached one in four.
Figures from the exam boards showed 25.3 per cent of exams were graded A, up from 24.1 per cent last year.
Girls continued to score better grades than boys in every major subject apart from further maths and foreign languages.
But despite fears from critics of the exam system, traditional subjects such as maths, German and physics did not see another slump in popularity.
Jim Sinclair, director of the Joint Council for Qualifications, which published the results, paid tribute to the hard work of students.
"The improvement of the results at A-level reflects how well students have done this year," he said.
"Candidates who have worked hard are getting the results they deserve.
"There are many positive signs and improvements and some of the highlights are the continued upward entry trend in mathematics, the physical sciences also seeing an improvement and modern foreign languages remaining stable."
Overall, 96.9 per cent of candidates taking A-levels this summer achieved at least a grade E pass - up from 96.6 per cent last year.
But the soaring numbers achieving A grades will fuel the debate over whether the exams are too easy to be a useful measure of ability for the brightest pupils.
In 1997, only 15.7 per cent of A-level exam entries were given A-grades.
Professor Alan Smithers, from the University of Buckingham, said: "I think the A-grades hitting 25 per cent is a matter of concern because it does not distinguish sufficiently well at the top end."
Universities have complained that so many teenagers score A's that they cannot rely on A-levels to identify the truly outstanding candidates from the merely very good.
The figures for England, Wales and Northern Ireland were released by the exam boards in London.
Liberal Democrat education spokesman Stephen Williams called for a review of A-level standards in the light of today's results.
But schools minister Jim Knight said one had been carried out three years ago, adding that it was a "real shame" pupils' performances were undermined each year by the debate about standards.
The percentage of entries gaining an A grade in Northern Ireland has risen by just under 1 per cent to a third.
This compares with a quarter achieving the top results nationally.
The province's Council for the Curriculum, Examinations and Assessment (CCEA), said the improvement was due to excellent performance in mathematics, languages and science.
Girls are still outperforming boys.
CCEA chief executive Neil Anderson said: "Having had a close look at the detail of the results, it is clear that the steady improvements we are seeing across the grades has once again been driven by exceptional performances in subjects such as mathematics, languages and sciences.
"We see better grades being achieved because of the sustained effort (of students)."
There were 30,815 entries for A-level, a decrease on last year.