As someone who used to go to high school before graduating in may:
1: Don't stress about stuff. It's gonna be like middle school. You ha e your teachers that are chill and more down to earth, then you have those who stress about everything. Its the same old rodeo.
2: Do your assignments on time. Font hold off in thr last minute. If your in physical, it can tank your grade. If your digital, it can pile up. But hey, better late than never I suppose.
3: Find some clubs or friends to occupy the time. It's gonna be for some hours each day, so you might as well get some people to talk to and spend the time with before the clock rings out. Hope this helps, and good luck!

thank u