It is a stressful time of year for many GCSE pupils sitting exams.
Pupils at Lea Manor High School in Luton have been taught the wrong module for one of their GCSE exams.
RE students, who are now waiting for their results, found out they had spent the year learning the wrong syllabus just before sitting their mock exams.
On behalf of the performing arts school, Luton Borough Council said in a statement: "This was as a result of human error for which the member of staff concerned takes full responsibility."
Parent Steve Thompson told BBC Three Counties Radio about the moment he found out about the blunder: "My daughter came home quite irate and annoyed. They'd been taught the wrong subject.
"It came to light when they were given a mock paper to revise and she said 'Miss we haven't been studying this,' the teacher then rushed out of the room to seek advice and that's when the embarrassment set in."
Once the school realised the mistake Steve said his daughter's class were given a two day 'crash course' in the modules they should have been studying.
"Crash course, it was more like a car crash. You can't teach nine months syllabus in two days. It's impossible!"
Steve said there was a lot of disbelief and anger amongst the pupils: "They were told if your marks aren't good enough you can re-sit it next year but the point of them doing some of these exams in year 10 is to take pressure off them during their main year of GCSEs in year 11," he said.