I was in the same possition as you when I was 13, I decided that I would save untill I was 18 to see where that got me. I was 18 in May and decided that I would take a year out so I will be off to uni in sept 2010 however untill then I am doing my PPL. I have been given a job at my old school which will mean i can get more money for flying and uni and still have time to read the books and fly etc!
Hope this helps!
Tom