Exam chiefs today suggested it may be time to "crank up the standard" of A-levels as record numbers of students learned they had scored top grades.
As more than 300,000 teenagers around the country were waking up to their results, national figures, for England, Wales and Northern Ireland showed that the pass rate had risen again - for the 27th year in a row.
But teachers leaders' warned that new, tougher A-level exams could spell the end of record pass rates, and next year could see the first fall in decades.
As students were celebrating today, thousands were left facing a desperate scramble for for the last remaining university places, following an increase in applications this year.
Figures published by UCAS today showed that 135,114 students were already eligible for clearing this year, because they have not met the grades required for their chosen university, have chosen not to take up an existing offer, or were not holding an offer.
More than one in four exam entries have been awarded an A grade (26.7 per cent), and more than three quarters (75.1 per cent) were given at least a C.
The overall pass rate (grades A-E) was 97.5 per cent, a 0.3 per cent increase on last year, according to data published by the Joint Council for Qualifications.
Jerry Jarvis head of the Edexcel exam board said the awarding bodies had been engaged in "lots of discussions as to whether the grading system is capable of differentiation".
He said that many of the UK's leading universities were saying they have difficulty in choosing between applicants in certain subjects.
"I think it's a discussion that needs to be had.
"There's no question about it, it's a discussion about the value of the A-level, it's still a hugely trusted qualification.
"More and more students are making the grade, it's a consequence of success rather than a failure of the system itself."
Greg Watson, head of the OCR exam board, accepted that it may be time to "crank up the standard" to pick out the very best students.
A-levels are changing from September with the introduction of more analytical final exam questions and an A* grade.
The A* grade would only be given to students who achieved a score above 90 per cent.
He said: "There is a need to create some greater difference at the top end.
"When we sit here next year there will be a smaller category of students who have cleared the highest hurdle."
John Dunford, general secretary of the Association of School and College Leaders, said: "The standard of those exams will be more difficult."
When asked whether there was a need to shake up courses, he said: "Well that is going to happen anyway. The A-level next year is very different to the A-level this year."
Mr Jarvis also said students could be given marks as well as grades in the future.
He said: "We are looking at ways of discriminating or ranking figures quite regularly in discussions we have.
"In the future we may see complementary measures of performance.
"Grades have been around for a long time, grades have a very strong brand, the public have a feel for what is meant by grades.
"Comparing performance year on year is very important, for A-levels particularly, there's a great public perception and understanding of what it is.
"As grades themselves give us difficulty because of the increasing pass rate, we will continue to look at complementary ways of doing this."
The results show a disparity between grades achieved by pupils at private and state schools.
This year, more than half of entries from fee-paying schools were awarded an A grade, compared with just over a fifth of entries from comprehensives.
The figures show traditional subjects are still firm favourites for A-level students, with English and maths again the top choices.
There were an extra 7,882 entries for maths this year, and an extra 1,382 entries for further maths, compared with last year.
The statistics also show the tide is turning in science subjects, with an increase in the number of entries for chemistry and physics.
This may be due to a Government push to encourage pupils to take these subjects, and could also suggest students are turning their backs on so-called "softer" subjects.
There has been a big drop in the number of students taking general studies, PE and performing arts.
Languages also saw a slump in popularity this year, as entries for both French and German fell, although entries in Spanish, and other languages such as Chinese saw an increase.
Girls are still outperforming boys, the figures show, 27.6 per cent of entries from girls were awarded an A, compared with 25.6 per cent of entries from boys.
Dr Dunford said later that the introduction of the new "harder" A-level and the A* grade meant it did not make sense to recalibrate the system at this stage.
"Next year's A level papers will be very different than this year," he said.
"No further changes in the grading should be contemplated until we see the effect of the A* grade and the harder papers. Any changes to the grading system are confusing for employers and make comparisons impossible between the qualifications of applicants of different ages, so changes must be kept to a minimum."
Schools minister Iain Wright said the results reflected the hard work of pupils and teachers.
He said: "Critics who belittle better results and infer that the only way to measure a successful education system is by young people failing A-levels are insulting the hard work of students and teachers and the great support that parents give their children during these difficult qualifications."
Shadow universities minister David Willetts, said: "I congratulate all those who have received their A-Level results. Their success reflects an enormous amount of hard work.
"It is tragic that ministers are now blocking the path to university for so many of them.
"The Government first reduced the number of university places, then offered only unfunded places and are now threatening to fine universities that over-recruit. They said they wanted half of all young people to go to university by 2010, but now they are blocking progress towards their own target."
Dr Mary Bousted, general secretary of the Association of Teachers and Lecturers (ATL) said: "Today should be about congratulating students and teachers on their outstanding results, not belittling their achievements by criticising A-level standards."
She added: "It will be little short of a tragedy if all the hard work by this year's students is unrewarded by a place in higher education or a job.
"It seems particularly cruel to raise expectations and then dash them by failing to provide enough places in higher education for UK students.
"The Government will need to do more to support those who don't manage to get a university place this year."
Chris Keates, general secretary of the NASUWT teaching union, said: "The build up to the publication of these results has been marred by claims by some that exams have been dumbed down and that improved results are because so-called traditional 'hard' subjects are no longer being selected by schools and pupils.
"The notable increases in entries in subjects including mathematics, further mathematics, physics and chemistry expose the falsity of this claim.
"Following today's results the critics should eat their words."
Christine Blower, general secretary of the National Union of Teachers (NUT), said: "For all those critics who can't bear the idea that the improvement in A-Level results is attributable to the hard work of young people and their teachers, they should have a look at the trend in improvement in the so called 'hard' subjects of mathematics and science.
"It is quite clear that irrespective of the subject, there is no difference in the quality of the examinations and there can be no question mark about the effort put in by young people."
Kathleen Tattersall, chair of new exams regulator Ofqual, said: "Well done to those receiving their A- and AS-level results today.
"These are demanding qualifications that are highly regarded and will open doors of opportunities for the students, whether they wish to continue their education or enter employment."
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