It's gonna suck. They will want you to do all kinds of things you think are stupid and useless . BUT, do them anyway! Do what you need to do to move on to the next step. Use it to get ready for college. Keep in mind that you don't know as much as you think you do. You will think of this time for the rest of your life. So, at least try to enjoy it a little.
Dont get in anyone in the higher grades way, they'll shove you outta the way, be nice, make friends of higher grades in freshman year and friends of lower grades in sophomore year and stuff. Share lockers with siblings if they are closer to your classes. Carrying your backpack around is easier than visiting your locker sometimes, there is a lot more. BE NICE, but dont let people push you around