save up
Save up, wait for the G5 laptops, which you will want to buy when you go to college. Right now you can go over a friends house or use the computers if you school has them. Maybe your school will give out laptops soon since it is all the rage now a days, and it does improve kids learning. (saw this in person myself).
Now if you absolutely must have a laptop then i would say that if it is going to be schooling only, then 12 inch iBook. If you want games, then High iBook if not a PB. Also think about what else you want to do. Video, audio, make sure you get something that will last you some time, or wait, and get the new G5 PB when they come out in a year or two.