I would encourage you to try to learn from your middle school years. Time management, study skills, study groups, and be honest about whether you are doing your best effort. It is okay to ask for help, and now is a great time to make changes and improvements.
Also look at your overall activities and interests. Middle school is a great time to explore possibilities, but as you enter high school, you want to be narrowing down your interests to the ones you are most passionate about.