Everyone already gave good tips, so I’ll just put two down below. Don’t expect high school to be super easy. Certain classes may be easier than others, yes, but there are going to be classes that are a bit harder, at least. Those classes won’t be like middle school, you’ll have to put more effort into learning specific things. I learned this freshmen year, when I wasn’t prepared for the difficulties in my biology and geometry classes (I ended up doing well in both because I stayed after with the teachers when I had to, and I studied the material at home).
In addition, DO NOT PLAGIARIZE/CHEAT IF YOU TAKE AP COURSES. First of all, AP means that the course is college-level, so if you would plagiarize anything in college then you can get kicked out of the class or the college for it, so just don’t do it in your AP course(s) as well. Second of all, cheating on AP tests could result in getting a 0 as a grade or worse, and if you would get caught cheating on the AP exam then it will get cancelled (you won’t get a grade for it, so no college credit), and it may even lead to you never being able to take any other AP exams. Third of all, even if you would think that you’re very sneaky and would never get caught, you wouldn’t have time to cheat anyway. Tests are timed, and you will need all the time you can get. :^)
Disclaimer: I am not assuming that you would cheat or plagiarize, I’m just putting it out there just in case. It can be very tempting at times, so trust me, it isn’t worth it.