Keep doing what you are doing, fly as often as you can, keep volunteering and gliding, make connections and get known at the clubs.
Also ensure you nail your schoolwork, get high marks and be as educated as you can.
Plus get your ears firmly pressed to the ground over the next few years and be aware of all the likely organisations/guilds/companies that run scholarships, cadetships, internships, tagged/mentored schemes etc and the second something comes up that you can apply for get in there.
Oh and don't forget to be young, make some mistakes and have fun!
Good luck!