if you actually raced cat 1 you wouldn't give a shit about school, seeing as basically any school in the world would flow you a full ride scholarship.
OP, riding on sidewalks is illegal in most states, so ride in the street, and make sure you're confident and don't ride right on the white line, because not only is it slippery, but it'll cause some asshole drivers to buzz you, which can cause you to eat shit. Learn to use your front brake properly, as it offers you the most stopping power, and should be the one you squeeze in emergencies, so be sure you know how to pull it suddenly without doing an endo over your bars. other tips, learn to shift properly to maintain whatever cadence you feel most comfortable in. also learn to pedal through turns. also, if you want to get into racing, learn how to properly ride in a group.
if you're cruising around with friends, never, ever ride side-by-side in the street. it's annoying as fuck to drivers trying to pas, and illegal in many cases. while getting away with running stop signs is usually normal, don't be surprised if a bored cop pulls you over, as it IS your responsibility to follow every rule a driver does, which includes stop signs.
if you want to ride for exercise you want to ride two different types of rides on a regular basis. endurance rides, and interval rides. my weekly riding schedule basically involves two 30 mile rides, one 50 mile ride, and two interval rides. Intervals basically involve alternating sprints and rest, to basically "shock" your muscles into constantly developing. I'd recommend finding a short hill near your house and sprinting up it, coasting down, and repeating until you are near the point of vomiting. then have two rest days.
lastly, if you need any help with components, maintenance, or anything else, don't hesitate to pm me, as I am a huge cycling nerd, and can recommend you anything for whatever price you are looking for, and can fix basically any issue you have with your bike.
oh, and its only my second year racing cross, but cyclocross is possibly the greatest/worst thing you can ever experience. I'd recommend entering at least one race.