As far as I'm aware you might get charged for the exam by your school/whoever has entered you and maybe a chat from a teacher/tutor.
Right SECONDLY can people stop giving this guy a hard time? Let me just explain my situation.
I'm a musician and I've applied for a music related course at the University of Westminster in London. The University are MORE INTERESTED in my musical ability than my A-levels and because of that I've been offered a place if I can just get two C's at A-level. Everyone got me?
I currently study 3 A-levels and although I only need two of them I will be having a crack at all of them in case something goes drastically wrong in one of them. But in order to be classed as in 'full time education' I needed to take an extension course at the start of the year - out of the bunch offered I chose Critical Thinking which is an AS.
I DO NOT NEED IT FOR WHAT I WANT TO DO AND WILL PROBABLY FAIL IT
I got a U in the January exam (perhaps partly because I was suffering from a throat infection) and to bring the grade up considerably I would need to work for it. It's just added stress that I can do without in exam season.
So if this guy won't need the GCSE he might not turn up for LET HIM GO AHEAD HE DOESN'T NEED IT