Hi Omlaaay,
I find myself in an almost identical situation to yourself. I'm 14 at the moment and in Year 9 (take it you're in Yr10/11). Just chosen my options including an early GCSE and two AS Levels in Yr11.
I've got no real advice for you but I'll throw a few ideas on the table to help you out. I first flew aged 13 when I took a trial lesson. I'm now saving for a PPL and trying to get some part time holiday work down at an airfield somewhere (anyone who knows of any P/T work at Gamston/Netherthorpe could you please get in contact via PM please
). I'd say take a trial lesson because if you like it, then the thought of going flying again is good motivation for exam revision and a damn good reason to try at school.
Then there's getting advice. If you have a Facebook Account, add Captain Alan Carter, he puts alot of info up on his page and photos/vids from his job for all to see. He also gives advice when is asked and is a very good man for doing so. I went to a seminar called "Efficient Sector" hosted by two Thomson 757 FO's and it was very good. I got a lot of advice and continuing support from them. The £50 was very well spent.
I wish you all the luck in the world and hope that someday we'll both be working on the flightdeck.