The key is not to think about trying to sleep. If you keep thinking thoughts like, “I just gotta get to sleep or I’ll be useless tomorrow”, you’ll only stress yourself out. It’s actually good to let your thoughts wander when you’re tired because you’ll often wander right to sleep.
Odds are though, if you can’t sleep you just aren’t tired physically. You said after school you are exhuasted, well it’s probably just your mind is exhausted and your body feels the same way. I get that same thing after work. The best home-grown, Bona-fide way to solve that issue is as simple as it is challenging: exercise! I always, whether I feel like it or not, go for a mile walk after work. It not only eases my worktime stresses but also effectively uses up my excess energy. Motivation is the only problem with this, so you’re just going to have to force youself to get to it. It’s well worth it in the end, and I can fall asleep with no drugs or intoxicants in roughly a half hour almost every night because I don’t have the day’s stresses hanging over me and I am physically exhausted.