First off, congratulations on 'getting it' at your age, your off to a good start! At a younger age, especially when your in school, I would rely on knowledge more than gear, because of a lack of money for gear and also being prohibited from knives or lighters at school. Learn how to start fires with a flint and steel and by friction as well, as this is fun stuff to learn and practice. Learn to purify water through boiling and naturally made filters, etc. With that said, I have carried a ka-bar fighting knife and lighters at school through all of my middle and high school years without getting caught. Keep things to yourself and you won't be caught, because if you want a true survival kit, you will need plenty of things that a school will frown upon. As far as an actual school friendly pack is concerned, I would take a metal canteen with the cup for boiling water along some bottled water. A firesteel and tinder to catch a spark, Antiseptics, gauze tape, a few candles, 550 paracord, LED flashlight, a small razor instead of a knife, high energy protein bars, a tarp for shelter, a lensatic compass, appropriate seasonal clothing if its cold. thats just a few things i can think of off the top of my head. good luck to ya.