Nearly half of students (44.8 per cent) were awarded an A or A* in at least one subject, up by 6.3 per cent on last year, according to the Joint Council for Qualifications (JCQ).
Tuesday’s results come following a second year of disrupted learning due to the Covid pandemic.
Exams were cancelled and students assessed instead on a combination of mock tests, coursework and essays, raising concerns over grade inflation.
Overall, the proportion of entries awarded the top A* grade this year has surged to 19.1 per cent – the highest number since the top grade was first introduced in 2010.
Girls performed better than boys at the top grades, and female maths students overtook their male counterparts for the first time in the number of A* grades achieved, the figures for England, Wales and Northern Ireland show.
The Scottish Highers results are also being released on Tuesday.
The higher grades mean more students than ever have been accepted onto their first choice of university course.
A record 395,770 students will take up a place on their preferred degree, up 8 per cent from 365,500 in 2020, the admissions service Ucas said.
Students from disadvantaged backgrounds will start university courses in record numbers this year, according to the Department for Education.
Speaking to BBC Radio 4's Today programme Gavin Williamson, the education secretary, defended the government's approach to handling A-level results this year, after the chaos surrounding the algorithm system in 2020.
He said it was a year like “no other”, adding: "No other cohort of students have experienced a situation where they haven't been able to go into the classroom for a sustained period of time, not just once, but actually twice, and we have seen people having different experiences."
When asked how he planned to tackle grade inflation, the South Staffordshire MP reiterated that “we have been dealing with unprecedented times”.
In a separate interview with Sky News, Mr Williamson did not rule out using a teacher-assessed grading system next year, although he insisted the government's plan is to return to exams.
He said: “We’re very much planning to move back to examinations as a form of assessment, but we always have to have a contingency plan in place and that’s why we’ll be consulting in the next academic year on those plans.”
Teachers in England submitted their decisions on pupils' grades after drawing on a range of evidence, including mock exams, coursework and in-class assessments using questions by exam boards.
According to an analysis by Ofqual, some 6.9 per cent of students in England were awarded three A*s this year – compared with 4.3 per cent in 2020 and 1.6 per cent in 2019.
Last summer, the fiasco around grading led to thousands of A-level students having their results downgraded from school estimates by a controversial algorithm before qualifications regulator Ofqual announced a U-turn.
Instead, schools and colleges in England were asked to provide samples of student work to exam boards, as well as evidence used to determine the grades for the students selected, as part of quality assurance (QA) checks.
Random and targeted sample checks of evidence were also carried out after grades were submitted.
Ofqual said that student work from 1,101 centres in England – around one in five schools and colleges – was scrutinised by exam boards.
For 85 per cent of the schools and colleges whose students' work was scrutinised as part of QA checks, the regulator said the subject experts were satisfied that the evidence supported the teacher-assessed grades that were submitted.
It said the remainder were subject to further scrutiny, including conversations between subject experts and staff from the school or college.
Following this, "in most cases" the exam boards were satisfied with the original grades or with the revised grades which they submitted.
But Ofqual said that, at the time of writing its report, exam boards were in continuing discussions with "a small number of centres" and grades would be withheld for these schools should concerns remain unresolved on results day.
Dr Philip Wright, director-general of JCQ, said: "On behalf of JCQ and the exam boards, I would like to congratulate all students receiving their results today.
"The impact of Covid has undoubtedly provided a difficult chapter in their education journey and their resilience is to be applauded. We wish them all the best as they take their next steps in life.
"We would also like to express our sincere thanks to teachers, exams officers, heads of centre and colleagues, who have all worked exceptionally hard to determine grades this summer.
"Teachers used their professional judgment and submitted the grades and evidence in good time for us to check and award grades today. Their efforts will allow students to swiftly progress on to the next stages of their education, training or employment."
Geoff Barton, general secretary of the Association of School and College Leaders (ASCL), said: "It is important to understand that the system used to assess students this year is different from both formal exams and the approach that was used last year too, when an attempt to use an algorithm to standardise grades nationally went wrong and had to be abandoned.
"It is therefore invidious to make direct comparisons with other years and vital that we celebrate the achievements of this year's cohort who have had to endure so much over the past 18 months."
He added: "The majority of university applicants will now go on to their preferred university, and those who have missed grades and go through the clearing process will receive support from universities, schools and colleges to find a course which fulfils their aspirations.
"It will be important that universities provide educational and pastoral support to their new undergraduates given the extreme disruption they have faced during the course of the pandemic, and we are sure this is fully understood already."
Ucas said 91 per cent of applicants have a confirmed place at university, up from 88 per cent last year. In total, a record 435,430 students have a place, up 5 per cent on results day 2020, it said.
The record results mean there are likely to be fewer places available through the clearing process at top universities.
Clare Marchant, Ucas chief executive, said: “Universities have been flexible with their decisions to accommodate as many students as possible onto their first choice of course. Over the following days and weeks, we’re ready to help anyone without a place find the opportunity that’s right for them in clearing.”
Prime minister Boris Johnson congratulated students on getting their results.
He said: “I know it's been a particularly difficult year for everybody doing A-levels because of the pandemic and the conditions in which you've been working in.
“But thank you for persevering, and thank you to your amazing teachers.”
He added: "If you haven't got exactly the results you were wanting never mind, it happens to the best of us and there are plenty of options available through Ucas."
Additional reporting by Press Association
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