Top A-level grades have increased for the first time in six years, as teenagers in England, Wales and Northern Ireland get their results.
A* and A grades were awarded to 26.3% of entries - up by 0.5 percentage points compared with last year - with boys overtaking girls in top grades.
There was a fall in the top grades for 13 subjects in England with new content and now assessed only by final exams.
The number of university places allocated so far has dropped this year.
In A* and A grades, boys have moved ahead of girls, with 26.6% of boys getting these results compared with 26.1% of girls, reversing a 0.3% gap last year.
The change is significant because girls outperform boys at every stage of their education, and have been performing better at the top grades at A-levels for 17 years.
There have been suggestions this could reflect the introduction of the new style of A-level exam.
As results were being received, the Ucas admissions body said 416,000 university places had so far been confirmed - down 2% on the same point last year.
University applications from the UK and European Union countries have fallen compared with last year and there is a demographic dip in the number of 18 year olds.
Many universities, including in the prestigious Russell Group, will still have places on offer through the clearing system, which matches people looking for places with vacancies on courses.
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Pupils at a secondary school close to the Grenfell Tower fire in London received their AS-level results.
Four pupils from Kensington Aldridge academy died in the fire and 50 were made homeless.
But in this year's results, more than 40% of the pupils achieved A to B grades.
Head teacher David Benson said: "The pupils have been incredible."
Changes to the qualifications system in England mean 13 A-level subjects this year have been decided solely by final exams, with no link to coursework or AS-levels taken after the first year of study.
The overall results remain broadly similar to last year, with over a quarter of entries receiving top grades. The proportion of the highest A* grades has nudged up by 0.2% to 8.3%. The overall A* to E pass rate is marginally down at 97.9%.
But in those new-style A-level subjects, including history, English, psychology, physics, chemistry and biology, there were 0.7% fewer A* and A grades overall. Some 24.3% of entries attained the top grades in these subjects.
Exam boards said the fall in results reflected a lower-achieving group of candidates, rather than the exams being made "more challenging".
In previous years, when more candidates sat AS levels as the first stage of the exam, some poorer performing pupils would have been "weeded out", said Mark Bedlow, director of regulation at exam board OCR.
Leader of the ASCL head teachers' union, Geoff Barton, said that when AS-levels no longer contributed to final A-level grades, schools were increasingly likely to abandon the exam.
AS-level entries have fallen by more than 40% this year, and Mr Barton said he regretted this "narrowing" of options.
Testing new exams
But changes to A-level exams, including updated content, were defended by John Blake, head of education at the Policy Exchange think tank.
He said they had been designed to end a culture within schools of pupils repeatedly resitting exams to get the best grade. This was painful and time-consuming for teachers and pupils, he claimed.
"It led to less teaching time and made it harder to get a proper grasp of the subject."
But there have been concerns from pupils who have been the first to take these revised exams.
A survey of A-level students from the Student Room website found worries about a lack of textbooks and practice papers for the new style of exams.
Alex Scharaschkin, director of research and compliance at AQA board, said: "We do sympathise and understand it's an anxious time for students who are the first to go into these first qualifications."
He said some groups of pupils will have adapted to the changes easily, while others would have found it more difficult.
Schools minister Nick Gibb said: "We want everyone, regardless of background, to be able to fulfil their potential and for many, A levels are the pathway to a university degree.
"The increase in entries to facilitating subjects, those that give students the greatest choice of options at university, mean even more young people will have access to all the opportunities higher education provides.
"There has been a strong uptake in core subjects, such as maths, which continues to be the most popular A level with maths and further maths having nearly 25 per cent more entries than in 2010."