While the school has stood by its disciplinary procedure, the students insist that there has been a mix-up and they were in another class waiting for a teacher to arrive. They have also insisted that the school caretaker spoke to them while they were there.

"The whole thing is ridiculous, " said Susan Delahunty, Edel's mother. "Edel was absolutely devastated by the whole thing and it affected her exams badly. She has never been in trouble with the school before and when I heard she couldn't graduate, I couldn't believe it."

Edel and her classmates claim that they were prevented from collecting books for their exams from the school and only got them through the kindness of one teacher.

"She was crying on the first day of the exams at the thought of going back there, " said Delahunty. "If they had been mitching or had done something wrong, I might be able to understand it, but they have been treated incredibly unfairly. People have been asking if it's really true, but even some of the teachers have backed them up and said they've been treated badly."

No one at Trinity Comprehensive was available for comment, but a spokesman said that the students have been treated according to school policy. "The school acted fairly within the proper disciplinary procedures, " he said. "The parents were informed and were made aware of the procedure."

Delahunty denied that she was ever contacted by the school. She is writing a formal letter of complaint to the board of management and said she is seeking advice from a solicitor.