Paul Sweeny, a student of consistent "high calibre" according to his headteacher, collapsed from exhaustion in mid-exam two years ago. Since then, Bexleyheath comprehensive school in Kent and the Sweenys have been fighting to persuade the Oxford Delegacy of Local Examinations to increase his D grade.
Headteacher Malcolm Noble has criticised the appeals system and called on the School Curriculum and Assessment Authority to investigate the matter.
The board was severely criticised by the Independent Appeals Authority for School Examinations, which ordered the Delegacy to reconsider the case, even though it had already increased Paul's grade from E to D.
The authority was not satisfied the board had taken into account Paul's medical condition. His marks were raised a second time, but not enough to improve his grade. The IAASE was finally satisfied that the board had paid enough attention to the illness and closed the case.
Paul, now a professional snooker player, was awarded grade Bs in a second A-level and an AS-level. His school predicted, on the basis of two years' course work, that he would get a B in A-level history.
But on June 10, 1993, he collapsed in the middle of his first history paper. Paul was unconscious for 30 minutes and taken to Dartford Hospital, where doctors attributed his collapse to exhaustion.
He managed to take the second history paper, but his doctor told the exam board: "Paul managed to complete the rest of his exams, but it is my opinion that he would still have been suffering the effects both of this episode and general exhaustion which precipitated it."
Mr Sweeny, who, with his wife, serves on Bexleyheath's governing body, said: "The IAASE upheld our appeal. We naively expected the Delegacy to accept this without bias. While the Delegacy met the IAASE's requirements, they appear to treat the decision with contempt.
"How can the Delegacy, as a non-medical institution, consider their opinion more relevant than that of the medical profession when the foundation of the appeal is based on medical grounds?" Mr Noble said the appeal had led him to conclude: "Any candidate for an examination who enters and actually sits the paper in an unwell condition is worse off than being entered and not sitting the examination at all."
Both the Sweenys and Mr Noble, who were not allowed to see Paul's exam scripts, believe the appeal system favours exam boards.
Brian Arthur, secretary to the IAASE, said if the appeals authority had been dissatisfied with the outcome of the appeal, its chairman, Dame Elizabeth Anson, could have referred the matter to SCAA, but she had chosen not to.
Peter Clare, acting secretary to the Delegacy, said: "As far as the board is concerned the matter is closed. "