Yes, but only once! This may be the land of the free, but we're not handing out college credit to anyone with a computer. You'll get one chance to retake each unit test and final exam, and then that’s that! Be sure to take your tests after you’ve studied for them, and be sure to take them somewhere with a stable internet connection!
P.S. If you decide to retake an exam, your previous score will be erased and the most recent score will count toward your grade, so be sure you're ready to part ways with your first score.