A girls' school in Oxford has hit out at examiners after four A-level students received lower grades than they deserved. The results cost three of them university places.

Headington School, in London Road, Oxford, is demanding the reform of the marking system after mistakes by the Associated Examining Board.

Two students - Michelle Denninger, 19, of Balfour Road, Blackbird Leys, and Amy Shields, 18, from Blewbury - missed out on places at Oxbridge colleges because of an alleged "rogue examiner".

Hilary Fender, headteacher of Headington School, said: "I am appalled by what happened to these students and what we had to do to put things right. The system has let them down very badly." The two girls each needed A grades in English to stand a chance of taking up places at Oxford or Cambridge - but both were awarded Bs.

Each had scored As in coursework and in one exam paper but Es in the "prescribed text" exam - generally regarded as the easier written paper.

The school, suspecting something was amiss, paid £290 per pupil to have the exams re-marked. Last week they were told their grades had been improved by one.

Fellow students Adrianna Jones, 18, from Hampshire, also had her grade C increased to a B, and Vivienne Crias, 18, from London, was awarded a C instead of a D.

But for most of the students it was already too late. Michelle took up a place at London University after failing to get sufficient grades to study English at St Anne's College, Oxford.

Amy decided to take a year out in India and was resigned to going to Nottingham University, instead of Cambridge, next year.

Meanwhile, Adrianna was taking a £22-an-hour crammer course in a desperate bid to improve her grades to go to Edinburgh University next year.

Michelle's mum Hazel said: "She could not believe it when the results came in and she had not got her A - she had always been the best in the class.

"This sort of thing can really dent your confidence in yourself. We are delighted the results have been corrected, but we would like a written apology from the exam board."

Amy has now applied to go to Cambridge next year after her father Calvin, an airline pilot, sent an entrance form to India in the nick of time. Her mum Linda, a secretary at Moulsford School, near Wallingford, said: "Amy was so upset - she thought it was her mistake. There should be a back-up system. There seem to be too many mistakes going on."

Now the £11,000-a-year independent school is demanding changes both in marking exams and the handling of appeals.

Headteacher Mrs Fender, who blamed the errors on a "rogue marker", added: "So few teachers want to get involved in marking because it is so stressful and the pay is so bad.

"The long and short of the appeal system is that it takes a long time to work, when time is of the essence to secure university places."

George Turnbull, spokesman for the examining board, said Britain had one of the "most thoroughly monitored exam marking systems in the world". He pointed out that only four out of 27 Headington School students who appealed against their grades had them improved.

He said: "It is not true there was a rogue marker but one module was thought to have been quite severely marked.

"I can understand that if a student gets an A instead of a B, it makes a world of difference, but we are talking about very subtle changes in marks here."

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