Hi there. Your case is terrible and there has been several similar cases in Spain lately.
The first step is to denounce the facts to the spanish police for scam and study if we could reach some responsability or help with spanish culture department ( Ministerio de Educación)
In the other hand, try to manage with Cambridge to repeat exams even paying new fees in order not to lose one year time.
To do that, I recomend you to speak with a group of parents and contract a barrister in Spain together to sue the owner at court, criminal and civil court, and manage with Cambridge and culture department.
Also you could ask for media help, callig papers and radio to denounce your case to get more help from spanish goberment.
I will be here if needed, thank you.
José M spanish solicitor, barrister.