Bitter-sweet celebrations broke out at two private schools this week after nearly half of their pupils had their English literature GCSE results upgraded by Britain’s largest exam board.

Some 82 per cent of pupils entered for the exam from Haileybury school, in Hertford, had their scores improved on appeal. A total of 51 of the 122 pupils entered gained better grades as a result.

One improved by 63 marks out of the 350 available, taking her grade from a C to an A. The changes are among the most dramatic ever to be reported to The TES.

Haileybury, where boarding fees are pound;23,085 a year, has praised the AQA board for allowing all pupils’ papers to be re-marked. But it says the results raise serious questions about the reliability of marking. Up to 12 students decided against studying English literature in the sixth-form after receiving poor initial grades.

Epsom college, the Surrey boarding and day school, said almost all its pupils had had their marks for separate AQA exams in English and English literature improved on appeal. As a consequence, 40 per cent of the school’s grades were raised in English literature. Forty-eight pupils’

grades were raised in English. As The TES revealed two weeks ago, Haileybury was one of several leading private schools to appeal about what they claimed were serious marking discrepancies.

Haileybury’s English literature results had slumped from 49 per cent of pupils achieving A* or A grades last year to 30 per cent this year. The rate in English language this year was 50 per cent. Teachers were the same for both subjects.

The school sent a sample of 15 English literature papers to AQA to be re-marked. Of these, three were upgraded. AQA then agreed to re-mark all of Haileybury’s scripts. One student improved by 63 marks on appeal. Another went up by 53 marks; two went up 41 marks; while 37 students went up by 20 marks or more.

As a result, the proportion of Haileybury pupils achieving A*A increased from 30 to 45 per cent, while the school’s overall A*A rate rose from 56 to 58 per cent.

David James, head of English, said: “Staff and pupils are obviously hugely relieved that some very obvious wrongs have been put right.

“That said, any system which allows these results to go through in the first place does not inspire much confidence. I would hope that, in the future, there are more effective checks and balances in place.”

Epsom college described the changes as a “very major admission of error”, and said it was asking the board for its papers to be marked by a senior examiner in future.

Some schools have fared less well, however. Our Lady of Sion school, in Worthing, west Sussex, is unhappy after its proportion of A*s fell from 36 per cent to 11 per cent this year, even though English results rose.

The school only appealed on the grading of one pupil’s papers. The grade was not changed.

An AQA spokeswoman said: “The marking of examination papers is a thorough and rigorous process which is carried out to the very highest standard.

“However, it is important that awarding bodies have systems and processes in place so that schools and colleges can contact us if they have any queries about results. Everything is done to ensure we act in the best interests of all our candidates.”