The proportion of A-levels awarded at least an A grade has fallen for the second year in a row, official figures have revealed.
A total of 26.3% of entries scored an A or A* this year, down from 26.6% in 2012 when the pass rate at both grades fell for the first time in more than 20 years.
The 0.3% drop is believed to be the second biggest fall in the history of the exam.
The number of A* grades achieved also dipped, with 7.6% of pupils reaching the top grade compared to 7.9% last year.
However, the overall pass rate at A*-E rose slightly by 0.1% with some 98.1% of exams given at least an E compared to 98% last year.
More than 300,000 school leavers in England, Wales and Northern Ireland are receiving their results today.
A record number of applicants - 385,910 - have already been accepted onto university courses as interest rallies after a drop-off in 2012 when fees trebled.
The national results picture shows boys outperformed girls at the very top and widened the gap, with 8% achieving an A* compared to 7.4% of girls.
Girls are still slightly ahead on A* and A grades combined but their results fell half a percentage point this year to lessen the difference.
There was also a major contrast between the subjects picked by each gender.
For example, girls accounted for seven in 10 entries in English but in physics, four in every five pupils were boys.
Officials said the gender gap had been present for some time but had "extenuated" this year.
The fall in the overall number of top grades came as rising numbers opted to study science and maths at A-level.
It appears to bear out the suggestion that more youngsters choosing to take traditional subjects to help their chances of a university offer could fuel a slight fall.
Biology, chemistry and physics accounted for 17.8% of all entries, up from 17% last year and 15% in 2009, according to the Joint Council for Qualifications (JCQ).
One in eight (12%) were for maths and further maths, up from 11.5% in 2012 and 9.8% five years ago.
A-level economics also appears to be enjoying a surge in popularity, with entries up 50% since 2007 and at 26,139 in 2013.
However, young people are still turning their backs on modern languages with both French and German entries down again this year - although Spanish bucked the trend.
JCQ director Michael Turner said: "The continued rise in subjects such as the sciences, mathematics and the extended project, will be welcomed.
"However, that so few students take a language A-level is disappointing and, though Spanish continues to show growth, the overall trend remains downwards."
Neil Bentley, deputy director-general of the CBI, added: "It's clear students are being savvier in the face of higher degree costs and a tougher labour market, by taking subjects which maximise their future job chances.
"Higher take-up in science and maths is good news, given the critical skills gaps in key sectors, like manufacturing and engineering, which drive long-term growth."
Admissions service Ucas said 31,600 more applicants had been accepted by UK universities and colleges than last year, a rise of 9%.
Around 345,300 were accepted by their first choice. Another 98,740 are waiting for their results or decisions and 145,730 are eligible for clearing.
Ucas chief executive Mary Curnock Cook said: "Demand for higher education has recovered after a dip last year and universities are keen to accept qualified applicants."
Hackers attempted to sabotage the Ucas website on Wednesday night but were successfully blocked and no personal data was obtained.
Universities and Science Minister David Willetts said the Ucas figures showed school leavers were not being put off higher education but stressed there are also now more options.
"We've doubled the number of apprenticeships and so young people now have got a real choice," he said.
"They have got the apprenticeships route with vocational qualifications, they have also got the university route, which is more flexible than ever before, and that is investing in our nation's future."
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