You should definitely post them on GitHub if you think they are interesting or if you feel like they showcase your skills. There are a few good ways to approach this:
One good rule of thumb is that as a student you don't need to post anything that you spent fewer than two weeks on. So if you have a bunch of weekly assignments that had you practice using various data structures, algorithms, or other concepts, those probably won't be very interesting to recruiters. Either they are tiny projects or you were given a bunch of pre-written starter code, neither of which are that impressive. However, if you have a final project or a midterm that you worked on for several weeks, that is more likely to show off your knowledge.
Another way to approach it is to think through the classes you took and list the coolest thing you made in each one. For example, my very first programming class made Minesweeper as the final project, and while my Operating Systems class made several cool things, I was really into the project where we wrote our own shells. Since you likely took classes in different topics, using this approach will show a wide variety of projects.
Don't feel like you need to specify that they were assignments in the description. It doesn't matter at this point, you wrote some good code and learned things in the process. It would be the same if they were pet projects that you chose yourself.
Do make sure to include your GitHub url on your resume. It shows professionalism and that way recruiters don't need to email or call you to get it.
Good luck!