The long-awaited call came as I was wandering through the wine department of the French hypermarket. It’d been two-and-a half-hours since the reporting of A-level grades, so I knew that there must have been a problem - good news travels fast.

“Well?” I breathed into my mobile.

“Do you want the good news or the bad news?” my son Alex asked.

First the good: he’d achieved two of his predicted grades and a distinction in the English Special paper, but he’d been awarded a C grade rather than the predicted A in English. I tried to console and reassure him, then spoke to my husband who was with my son when the results were announced. He said Alex had come out of school shaking and almost in a state of shock. They’d made some long and expensive phone calls throughout the day to be told what they’d feared - that Alex had not only lost his place at Oxford, but also his insurance place which required a B grade in English. The news had been confirmed by a rejection letter in the post the next morning.

My husband joined me on holiday the next day, looking tired and drawn. He had not slept the night before, worrying and wondering what could have gone wrong. We had previously arranged for Alex to join us four days after the results in case there were any loose ends to be tied up. He spent a sombre and depressing weekend alone, looking through his A-level English texts, trying to figure out where things went awry. His school had told us he was the best English student they’d had in five years and all his coursework had been at grade A.

Next day we made more expensive phone calls to Alex’s school, trying desperately to plan a positive course of action. We decided to apply to have the paper remarked - but that couldn’t happen until late September. The headteacher at Alex’s comprehensive assured us that he and the school would do everything they could to help.

Alex arrived on Monday night for what was to have been a grand family celebration of his academic triumph. My father, an English professor at an American university, was bitterly disappointed but put on a brave face. We all tried to keep the holiday mood light and cheerful, but the gloom was almost palpable. My parents flew back to America saddened by the week’s events and by their grandson’s uncertain future.

When my husband and I returned from seeing them off at Toulouse Airport, Alex was waiting by the gate. He made us both get out of the car and stand against the wall. “Imagine you are outside a school,” he said, “and lots of teenagers are coming out with their parents, some dejected, some ecstatic. I come out and leap in the air with a huge smile on my face and both thumbs up.”

He’d had a phone call from a friend looking after our house who had picked up a message from his school on the answerphone. His C grade was a mistake, he’d been awarded an A, and he had been reinstated at Oxford through clearing.

Returning to England we all felt we wanted some answers as to how this mistake had happened. We assumed that a letter of explanation would be waiting, but there was nothing but a revised grade slip reporting the change. I rang the Associated Examining Board in early September and was told that someone would ring me back the next day.

The head of examination services, Terry Davies, said that, as far as he could tell, Alex had simply been given the grade of the person above him in the list. He had no explanation about the delay in reporting the error, when it had been his understanding that the mistake was discovered on the day the results were sent out.

On Saturday, September 13, we received a letter from the AEB from Mr Davies to my son’s school, and copied to us. In it he gave a new reason for the error, which was that the marks were incorrectly added up in July. Incredibly, the marking wasn’t checked or the mistake discovered until August 14, after the marks had been released.

While we accept that errors inevitably occur, we can’t accept the lack of checking before results are sent out and, second, that candidates are not immediately telephoned and told of their correct grades. Major decisions which will affect children for life are taken on the day that results are announced. If our son had not been taking a gap year he would have certainly lost his place at Oxford.

One possible reason for the lack of telephone contact could be that these kinds of errors happen much more often than any of us suspect (even people like myself who have worked in education for 25 years and marked public examinations).

While we have not ruled out legal action, nothing could bring back what Alex lost during those eight days of anguish. Not only the telephone bills and the ruined holiday - but the heart-breaking fact that my son missed his moment of joy at school with his friends. When they were out celebrating, he was alone in his room. He got what he deserved in the end and we can only hope that sharing our experience might help to prevent another child having to suffer in this way.

Miranda Preston is senior lecturer in education at The Chichester Institute of Higher Education, a college of Southampton University.