The number of exams awarded an A grade or higher has fallen for the first time in more than 20 years, while boys have finally overtaken the girls in the number of A*s being achieved, official figures revealed on Thursday.
In total, 26.6% of the exams were given an A or A*, down from 27% in 2011 - a record drop of 0.4%.
It is believed to be the biggest fall in the history of A-levels. The last time it dropped was between 1990 and 1991 when it decreased to 11.9% from 12%.
The pass rate at A grade also stalled in 1996 and 1997, when 15.7% of exams were awarded at least an A.
Thursday's figures, published by the Joint Council for Qualifications (JCQ), also show that fewer A-level exams achieved an A* this year.
Around one in 12 (7.9%) exams were given the top grade, which is awarded for the third time this summer, down from 8.2% in 2011.
Boys overtook girls at A* grade for the first time, with 8% of boys' entries attaining the top mark, compared to 7.9% of girls'.
Thursday's figures also show that the overall A* to E pass rate has risen for the 30th year in a row.
Some 98% of exams achieved at least an E, compared to 97.8% last year.
Around 335,000 students in England, Wales and Northern Ireland are receiving their A-level results today.
But while many will be celebrating, others still face a scramble to secure a university place.
Initial figures from UCAS show almost a 7% drop in the numbers of students who have already had their places confirmed.
Michael Turner, director of the JCQ, which represents exam boards, said: "Today is about celebrating the successes of our young people and recognising the hard work that has gone in to achieving these results.
"They, and their teachers, can be proud of their achievements.
"The STEM subjects continue to rise, with mathematics, biology, chemistry and physics all in the top 10 most popular subjects.
"Over the next few years, it will be interesting to see if, with the existence of the English Baccalaureate, the continued decline in students taking a foreign language is reversed."
Ed Dorrell, features and comment editor at the Times Educational Supplement, told the Huffington Post UK the change was "insignificant".
"Ofqual has changed the rules slightly in the way they have changed the marking in a bid to try and reduce grade inflation. The actual drop itself is actually pretty insignificant. All we're looking at today is a small change in the system.
But, he adds, the system will always be attacked by critics.
"When the number of A and A* grades go up, the system is attacked by people who say the exams are getting easier. When the number goes down, teachers and pupils are criticised for not trying hard enough or aren't as bright as they used to be. It's very difficult to do well in."
"The A-level is still a world currency and the envy of many. It is a huge success. We really need to stop having a go at it."