You will need:
Folders
Notebooks
Cleanliness
Organizer
Sticky notes
Calendar
If you have 9 classes, get one folder for every three, so you have 3 folders in total.
You should have at least one subject of a notebook dedicated to each class. Don't put notes of multiple classes in the same subject. It can mess you up and leave you missing material.
Organization "starts at home." Keep your desk clean, your room clean, your locker clean. Make sure you know where everything is. Keep a routine. If you come home at 3:30 pm, get comfortable and find a time when you can do homework. If you need to watch tv for an hour, do it first so you have time for your scheduled ~homework break.~ This means that at 4:30 pm, you should be going crazy getting your homework done! Go you!
An organizer is essential. You can keep a tiny one that fits in your pocket or in an easily-accessible part of your backpack. Ideally, your organizer should list the day and give you enough lines so you can have at least one for each class. It's good to label each class, in the order they end, so you can tell even if you don't have homework in a class because its space will be blank.
If you have a locker, sticky notes are awesome. Even if you don't, you can stick them around your computer monitor, on your backpack, on your notebooks, on your organizer. Whatever works for you. If you have them, they should be as easily accessible as your organizer. They're not needed, but they're good if the teacher mentions an extra credit assignment or says something important before or after class and you dont have your organizer out yet.
If you dont have a calendar, c'mon! lol. Not only great for school and writing down when assignments are due and when tests are, but also good for doctors appointments, birthdays, other plans. It helps to keep you concentrated and sharp too! You won't be the one asking "What day is it?" you will be the one proudly proclaiming "IT'S MONDAY, SEPTEMBER 21st!"