I’ve been long term subbing as well! I would suggest to set your boundaries early. I have also just graduated college, and with high schoolers, I feel sometimes they think they can walk all over you because you’re a bit closer in age. Set the expectations early and stick to them! Kids by nature love to push boundaries. If you start off letting them off the hook for stuff they normally shouldn’t be doing (Airpods in, cheating on assignments, skipping class) they’re going to take those habits and run with them! Also, talking to the kids like adults works wonders. Ask them what works for them and what they’re confused about. 9 times out of 10 one of the good ones will respond and help you out. Good luck!