The proportion of students achieving grade A at A level is rising faster at selective and independent schools than at comprehensives and colleges, according to official figures.
This year, the percentage of students passing their A levels reached 97.2, up from 96.9 per cent last year. More than a quarter of students achieved A grades, up from 25.3 per cent in 2007 to 25.9 per cent.
But between 2002 and 2008, the proportion of students at independent schools achieving the top A grade rose by 9.1 per cent, compared with a 3.9 per cent improvement in comprehensive schools, figures from the Joint Council for Qualifications show.
The data also reveal that different regions of the country are showing widely differing rates of improvement, with students in the North less likely to achieve an A grade.
English and maths were once again the most popular A-level subjects, followed by biology, general studies, psychology and history.
As last year, the number of students taking further maths rose, this time by 15.5 per cent to 9,483.
Computing and IT were again among those subjects showing the biggest drops in popularity.
The number of entries in biology increased by 1,447, chemistry by 1,395 and physics by 630. The Campaign for Science and Engineering in the UK (CaSE) said this reflected a growth in the total number of A-level entries.
Hilary Leevers, assistant director, said: "It is important to remember that physics was the most popular science A level in the 1980s with more than 40,000 students, compared with today's 28,000."
CaSE was also concerned that gender imbalances had been accentuated, with 46 of the extra entries in physics being attributed to girls - in chemistry the figure was 239.
A total of 340,105 applicants had places confirmed on the morning of results day, according to the Universities and Colleges Admissions Service, up 9.1 per cent on last year.
Some 20 per cent of applicants were eligible for clearing, the same as in 2007. By 18 August, a total of 356,993 applicants had places confirmed (compared with 328,726 last year), with 4,767 having found a place through clearing (up from 4,448).
The Russell Group said it was increasingly challenging for universities to choose between highly qualified applicants, but that the introduction of an extended project and a new A* grade from this autumn would help.
Universities UK said: "Let's put this into context: approximately 3 per cent of all 18-year-olds taking A levels gained three A grades or more."
Wes Streeting, president of the National Union of Students, said the rise in standards was the result of hard work by students and their teachers. But he added that the NUS was concerned about the impact of the introduction of an A* grade on efforts to widen participation.
The University of Oxford said it would not be making offers based on achievement of the A* grade.