Teachers are intentionally bumping up students' predicted A-level grades to help them win places at top universities, the chief executive of Ucas has suggested.
The claim comes as universities are now "more flexible" with grade requirements amid intense competition to attract students, Mary Curnock Cook said.
She said some teachers had told her they were "over-predicting" sixth-formers' results to help them secure initial offers from universities that may be asking for high grades.
Ucas figures show that since 2010 there has been a 9 percentage point rise in the number of students predicted to score at least two A grades and a B at A-level. This stood at 63 per cent in 2015.
However, separate statistics show that students predicted to score such grades could actually be accepted with lower results, as many institutions are now accepting more candidates who fail to score their expected grades.
Last year, more than half of students accepted on to degree courses had missed their results by two or more grades, spread over three qualifications, Ms Curnock Cook said.
Speaking at a conference on higher education at Wellington College, Berkshire, she said: "I talk to a lot of schools and people who advise students, and in the past I would have said, 'Surely you wouldn't be over-predicting your students on purpose?', and actually just this last summer really, I had teachers coming back to me and saying, 'Actually, yes we would'.
"I'll show you why, because actually...the number who are being accepted with quite significant discounts on their offers and their predicted grades has grown quite a lot.
"52 per cent of A-level accepts have missed their grades by two or more grades over the portfolio of three [A-levels]."
Over-prediction of grades has always occurred, Ms Curnock Cook said, but she indicated that it is becoming more common.
But she added: "Offers are being discounted at confirmation time, and we can see that.
"We can see that because the lifting of the number controls has increased competition amongst universities to recruit students. You can see that happening."
Professor Michael Arthur, provost and president of University College London, said that his institution's standard offer is one A* grade and two As or three A grades. He added that last year, around "9 per cent or so" of students were admitted on slightly lower grades than their offers.
A Department for Education spokesperson said: “We trust teachers to act in the best interests of their students by giving fair predicted A level grades that accurately reflect their ability. Distorting grades would be unfair on the pupils involved and could result in universities having to artificially inflate their entrance requirements, rendering it pointless in the long run.”
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