The proportion of top A-level grades in England, Wales and Northern Ireland has fallen since 2021, but remains higher than in 2019.
About 36.4% of A-levels were marked at A* and A this year, while last year, 44.8% of exams were graded A or above.
It is the first time since 2019 that A-level grades have been based on public exams, after two years of cancellations because of the Covid pandemic.
Students are also receiving T-level, BTec and other results on Thursday.
The university admissions service, Ucas, said 65.3% of students in the UK who applied to university got into their first choice.
This year’s A-level marking system has been adjusted, so that grades reflect “a midway point” between 2019 – when 25.4% were A* and A grades – and 2021, when teacher-assessed grades led to a boom in top marks.
England’s exam watchdog Ofqual has said the approach was intended to bring grades closer to pre-pandemic levels, while reflecting “that we are in a pandemic recovery period and students’ education has been disrupted”.
Similar plans were put in place for Northern Ireland and Wales.
In Scotland, where pupils received their exam results on 9 August, the pass rate at Higher level fell to 78.9% – down from 87.3% in 2021.
Ucas, said 425,830 students have been accepted into university or college – the second highest number on record – but 20,360 students have not.
They are being advised to search for vacancies through clearing, which is where Ucas highlights them.
Ucas also said more students from the most disadvantaged backgrounds were awarded a place at university than in 2019, and that 71% of university applicants who took T-levels were accepted.
London School celebrated top grades
Students and staff at Langdon Park School, Poplar, are celebrating today after receiving their A Level and BTEC results, enabling many of them to secure their first choice university place.
Nick Langham, Head Teacher at Langdon Park School, said: “Overall the results in 2022 have seen a significant increase in the number of A*/A grades when compared to the last set of public exams. More students have secured their first choice university and the school’s vocational offer provides a secure route to university and apprenticeships.
“These results, particularly given the circumstances of the last two years, are testament to the hard work of our students and the terrific support offered by teachers, support staff, tutors and parents.
“Securing the appropriate university or apprenticeship is life-changing and I am very proud of the achievements of every students and this illustrates firmly our school vision and ethos.”