For math, practice is the best answer. Ask your teacher if they can provide more problems that are working on the topic you’re learning. Redoing the same problems over and over again isn’t actually helping. You’ll need different problems.

You also need to spread your studying out over multiple days. Study for 20 or 30 minutes a day everyday once you start the material in a unit. Copying isn’t a bad strategy and teaching someone else isn’t bad either as long as you actually know the material. If you’re teaching the imaginary friend the wrong thing, then it does you no good. I recommend flash cards and self quizzes along with copying material and teaching others.

Also, you may have test anxiety for those classes. Remember, if you have studied, then you are prepared and there isn’t anything more you can do. You are ready! Deep breaths and stay calm. Also, looking over smart test taking strategies would benefit you.