I love the Hurley bags. They have them on apple.com and in the Apple Stores. No matter what kind of backpack you ultimately end up with, I would still get a sleeve. I keep my MBP in an Incase sleeve, then I can throw it in my backpack (which is just a generic Nike backpack, nothing fancy but it's a pack that goes on my back and will carry my computer plus a whole lot of books and other junk) or any other bag I want to use, or I can just pick up the sleeve and go if I'm just running to Barnes & Noble or the library and want to take my computer but don't need a big bulky bag to carry around.
On another note, I see that you're in NC. I think you might be about the first North Carolinian I've seen on this board, was starting to think our lack of Apple Stores meant a lack of Apple users! I'm in Asheville, over an hour from the closest store and that one is in Greenville, SC. If you're lucky, you live in Greensboro, Charlotte, or Raleigh/Durham so you have a store nearby. Good luck in high school!