A dance association that entered more than 200 pupils for a bogus GCSE is being investigated for possible fraud by the exams watchdog.
The International Dance Teachers' Association offered its dance GCSE to schools, leading them to believe it was accredited as an exam board by the Qualifications and Curriculum Authority.
But the association has not received any such accreditation, and is not included in Section 96, the official list of awarding bodies able to offer GCSE exams.
Between 2003 and 2004, 210 candidates from more than 20 schools took the so-called GCSE. Their award is now worthless.
Twenty-one pupils at Canterbury high, in Kent, were due to take the exam this summer, and attended after-school dance lessons for 14 months.
Phil Karnavas, deputy head, said: "It stinks. The dance floor has been pulled from under our pupils' feet. I was led to believe it was a valid GCSE, because it was called a GCSE. That means something in education.
"Now the IDTA wants to sell it as an 'own-brand' GCSE enrichment experience. But that has as much value as a Blue Peter badge. We paid out a lot of money and, from an academic point of view, the course is valueless."
The association's registration forms and correspondence refer to the qualification as a GCSE. An introductory letter to the 20045 course mentions that the GCSE uses "the IDTA 'own-brand' specifications", but does not clarify this term.
Sue Brooks, dance teacher at Rochester girls' grammar, discovered the lack of accreditation one year into a two-year course. "I was worried what the school would say," she said. "If I had entered pupils for the exam, I would have been in real trouble. Fortunately I have talented students, so changing course hasn't been a problem. But it has been a lot of extra work for me."
Ms Brooks's school also paid for a training course, run by the IDTA, which she was told was necessary if she was to teach the GCSE. "It cost about Pounds 1,000," she said. "And I had to give up my time. I would never have done that if I didn't believe it was an accredited course. My paperwork says 'IDTA GCSE'. It doesn't say 'IDTA diploma'."
The QCA has launched an investigation. Its lawyers have advised that if the IDTA received fees for the qualifications, it could be open to charges of fraud.
John Skipworth, QCA investigations manager, said: "Nothing the QCA has said or done would have led the IDTA to believe that it could offer a GCSE.
Schools should look to see whether a qualification is offered by an approved body. It's a case of caveat emptor."
Keith Holmes, who took over as chief executive of the IDTA in June, is assisting the QCA with its investigation. He said: "There's never been an intention by the IDTA to deceive anyone. If there was any fraud, it was not done intentionally. Obviously, we can't backtrack and help pupils who've already taken the exam. But we're looking into compensation packages. We're very anxious to bring this to a satisfactory conclusion for everyone concerned."
Under guidance from the QCA, the IDTA has provided training to enable teachers to convert pupils to an accredited course. It has also offered advice for affected candidates.
Courtney McDermott, 14, is among the Canterbury pupils whose work has now been invalidated. She will take another exam board's GCSE this June, and will have to redo all coursework and performance assessment. She said: "I missed netball matches and stayed in during half-term to write my essays.
Now I have to start from scratch.
"I want a career in dance. I want to do dance A-level. But now my grade won't be as good, because I have to do an entire course in six months. My time's been wasted. It isn't fair."
But few professional companies expect performers to have dance GCSE, whether or not the awarding body has been officially accredited.
A spokesman for the Royal Ballet said: "It may be helpful if you're teaching in a school, or if you want to become a choreologist who notates dance steps. But, with any performing company, there is an audition involved. It's about talent. You don't ask dancers to supply GCSEs."