Plyometrics. Seriously. When I was your age I bought these shoes that wrapped around my hoop shoes and didn't have a heel (so they elevated my calf muscle). The goal was to add extra pressure to your muscles when you jumped and ran, so when you took the shoes off you were more explosive --it definitely worked. I'd wear those shoes and do squats while climbing stairs, jumping in them alone, running in them alone, etc.
Frog leaps also give you nice hops and endurance (position yourself like your doing a squat, but jump in the air and smack your thighs when you reach your peak and keep repeating, I'd do 3 minute intervals).
Ouch. I cringed just reading that.