Middle school comes with bigger responsibilities. School gets more challenging, there is more work, more classes, teachers expect a lot more from you and they give you more pointed feedback.
Time management and organizational skills can help you plan ahead and get the work down with less stress:
Know your class schedule: You don't have to memorize it. Keep multiple copies of it so you can refer back to it.
Know how much time you have in between classes
Where is your locker? Is it near your homeroom? Near your second period? Far from all classes?
What extra curricular activities do you have each day? Do you need a change of clothe or uniform? Do you need any equipment?
How many books are you required to have and are you going to have enough time between each class to visit your locker?
Keep your backpack and your locker organized
Organize your computer desktop with folders so you know where to go to find the right information
Use a daily planner/calendar. It is impossible to remember everything that you have on your day. Write things down. It is a good skill that you will need the rest of your life.
STOP - THINK - PLAN - DO