Read , Revise and Repeat!
You have to balance the school, work and additional curriculum. If you are really struggling with your classes, you have to abandon the school's work or additional curriculum until your grades are grown. You have to take your time priority. Remember: Your education is very important because it's the basis for your future success. First of all, it takes a good change, but after a while it becomes secondary and is easier to read. Few tips for you
Manage your time.
Make it clear in your mind what you need to do with the heading you read.
Eliminate electronic distractions.