The proportion of A-levels scoring the highest grades has risen for the first time in six years, but figures show that government reforms are beginning to have an impact on results.
National figures show that more than one in four (26.3%) of A-level entries scored an A* or A this summer, up 0.5 percentage points on 2016.
It is the first time the A*-A pass rate has risen since 2011.
The increase comes amid major changes to the qualifications, with the first grades awarded in 13 subjects that have been reformed, with a move away from coursework, modular exams throughout the course and the decoupling of AS-levels, making them more challenging for students.
Among these subjects only, results are down compared with the equivalent subjects in 2016, statistics from the Joint Council of Qualifications (JCQ) show.
When comparing 18-year-olds' results, the proportion of A* grades for these courses is down 0.5 percentage points to 7.2%, A*-A grades have dropped 0.7 percentage points to 24.3% and A*-E results have fallen 0.5 percentage points to 98.1%.
The 13 reformed subjects are art and design, biology, business, chemistry, computer science, economics, English language, English language and literature, English literature, history, physics, psychology and sociology.
The figures, published by the Joint Council for Qualifications (JCQ), also show that boys have pulled ahead of girls for the first time in terms of A*-A grades, and have widened the gap at the highest result alone (A*).
Overall, 8.8% of boys' entries were awarded an A*, compared with 7.8% of girls - a one percentage point gap. Last year the gap was 0.8 percentage points.
In terms of A*-A grades, boys are 0.5 percentage points ahead this year, overtaking girls, who were 0.3 percentage points in front in 2016.
The statistics, for England, Wales and Northern Ireland, also show:
:: The overall A*-E pass rate has fallen by 0.2 percentage points to 97.9%;
:: The proportion of entries awarded the highest result - A* - has risen 0.2 percentage points to 8.3%.
Figures showed a huge spike in the number of entries for a small range of subjects, including computing, with a 33% rise in the number of A-level students sitting the exam in 2017, compared with last year. This included a 34% increase in female students - 816, up from 609 in 2016.
There was a 12.8% increase in the number taking political studies, and a 1.7% rise in those taking Spanish at A-level.
But there were dips in the take-up of other languages - with a 2.1% drop in those doing French and a 4.7% decrease in students sitting German.
Elsewhere, entries for history - one of the most popular A-levels by number of students - fell by 8.1%.
Data showed a 3.3% increase in entries for maths, but there was a significant drop in those sitting English.
This included a drop of 10.2% in English language, 4.7% for literature, and 11.1% for the combined English language and literature subject.
Overall, entries for English subjects saw a 7.2% decrease.