Each program/school will be different. Some general things that are typically different:
-Sideline : knowing how to work the crowd, get them to cheer WITH you, knowing when to call certain cheers/chants during the game
-A focus on motions and visuals rather than stunt/tumbling difficulty
-Tumbling on a dead mat/basketball court
-A focus on school spirit: being involved in the community, pep rallies, growing the excitement and participation at your school in spirit days/events
-Seeing your team before/during/at school : you don't get to escape your teammates during school. You will see them for practice, in some of your classes, after school when traveling to games, etc. which can be a good and bad thing. Having your team be like sisters is fun, but sisters that spend too much time together can also fight.
-Traveling to away games: #schoolbus
Make sure you do not go in with the "I was an allstar. I can do this stuff in my sleep *hair flip*" attitude. Keep an open mind, as allstar is not better than HS or visa versa.....just different focuses. I would say for you to not focus on what skills you are doing/see others do in HS, but to focus on learning leadership within your school & having unforgettable memories with your teammates. (The life lessons rather than the skills learned)