Student David Webster was unable to go to University College London as a result. His father Roger Webster says £11,000-year Silcoates School in Wakefield failed to guide him properly in his geography coursework.
David, from Darton, Barnsley, obtained As in maths and further maths but only got a B in geography after he was marked down on his coursework.
Mr Webster, 50, a lecturer at the Royal Northern College of Music in Manchester, says the school should not have let his son submit the coursework.
David, 20, is now studying for a natural sciences degree at Durham University but his father is still pursuing the case and has spent thousands on legal fees.
Mr Webster said: “David was predicted As in all his subjects and has always done really well at school.
“He went to get his results and we had a phone call to say he had got a B in geography. It meant he couldn’t go to UCL as he needed three As.
“What had let him down was the geography course work that had been submitted. It came back marked E which was a shock to him and me as well.
“I told him not to panic and I would speak to the head. The head assured me it was wrong and he would ask for it to be remarked.
“All six on the geography course had lower than expected marks and the school said they would send them back to the exam board.They all came back unchanged.
“When I queried this with the head he apologised and said he couldn’t discuss individual cases.
“He still maintained the work was of a sufficiently high standard but said the appropriate marking criteria had not been met.
“I then spoke to the exam board who said the coursework did not meet the criteria set by the exam board. They didn’t question the quality of the work, just the structural content.”
Mr Webster went through the Silcoates appeals procedure but eventually got a letter saying the matter was closed.
He said: “I sought legal advice at an early stage and letters have been exchanged between my solicitors and the school.
“After spending a lot of money on fighting the case and sending a lot of correspondence we are now having to think what to do next.
“I am considering taking the school to court for failing in their duty of care towards David. We had a contract in place that they would provide education to an agreed national level and we say they have failed to do that.
“They say they are not to blame and the exam board did not mark the coursework correctly.
“We’re not interested in any compensation. I just want the school to acknowledge that they got it wrong.”
David who starts his second term at Durham later this year said: “I’m happy now, at Durham, but I still feel like I’m not completely detached from Silcoates.”
Despite numerous exchanges between the family, the school and the OCR exam board the case has dragged on for two years.
Headteacher at Silcoates, Darryl Wideman, said any “fault” lay with the exam board.
He said: “We utterly refute any suggestion that the teaching he received was not satisfactory.
“We submitted David’s work in good faith and have always believed it was worthy of higher marks.”