The Conservatives are warning that the gap between the independent and comprehensive schools is growing among the highest achieving pupils.
In independent schools, 30% achieve three A grades at A-level
Among pupils getting three A grades at A-level, the Tories say that independent schools are now almost 23% ahead - compared to 11% a decade ago.
"The government is simply not doing enough to improve social mobility," says Shadow Schools Minister Nick Gibb.
The A grade is now the most commonly awarded grade at A-level.
The provisional figures for pupils taking their exams this summer show that 25.2% of the A-levels awarded were grade A - more than the 24.3% of grade Bs and 23.1% for grade Cs.
But the Conservatives have highlighted the way that independent schools are stretching their lead among the A-level high-flyers
"This worrying gap in achievement highlights the need for urgent improvement in the state sector," says Mr Gibb.
The figures for exams taken this summer show that 30.1% of pupils in independent schools achieved three A grades - compared to 7.4% in comprehensives.
In sixth form colleges, 9% of pupils reached this level.
Among pupils in selective grammar schools, 24.5% of pupils achieved three top grades - compared to an average for all schools of 13.8%.
However, in areas where there is selection, the non-selective secondary moderns only achieved 1.8% of pupils achieving these grades.
But the Schools Minister Jim Knight said there had been an increase in comprehensive pupils scoring three A grades.
"It is true that the proportion gaining three A grades has not kept pace with the increase in selective and Independent schools, but that is because of the rapid expansion in the numbers taking them in comprehensive schools.
"These are schools which are opening up A-levels to pupils who would not have been given the opportunity years ago - we are interested in the many, not the few," said Mr Knight.
The A-level exam results also show the wide differences in the proportion of A grades awarded within subjects.
Among candidates taking English, 23% received A grades, but in maths 44% achieved the top grade. In music, 17% received A grades, but in economics there were 36%.
A higher grade is going to be introduced at A-level - the A* grade, which is intended to distinguish between the growing number of students who are awarded A grades.