I don’t personally attend college but i do take classes, but what you’re talking about are “adult ballet classes.” If you’re a senior in high school, you are probably eighteen or will soon be. You’re an adult now! Once you know where you’re headed for school, check out some local studios and see if they offer adult classes. If not, see if you can simply take a few of the older level’s classes.
The great thing about adult classes are they are in the morning, but this may not work the best with your schedule anyways. Good luck!