Why not contact your nearest flying club - ask them to keep you in mind should at any time, a pilot has a spare seat and is willing to take you flying.
I don't know how many times I have flown with 2 spare seats in the back. I for one am very enthusiastic to share the marvel of flying, with anyone who is interested. I know there are many more GA pilots out there who feel they same way.
Other than that, work hard at school and don't be detered by career advisers or teachers who tend to rubbish youngsters with such ambitions. Good luck!