What do I do if my parents won't let me have a hobby and just want me to study?

Studying is important so you can get into a good college and job. Try to understand that they are looking out for your best interests. Maybe try talking to them about how you feel and see if you can negotiate something, like if you get all A’s, you can join an activity. If that doesn’t work then try to see if you can join an academic club. Your last bet if that doesn’t work is to see if you can go study somewhere else besides home and get away for a few hours with “studying” (still make sure you study some if you do that option).