How do I start a friendship with someone?

Since you have classes together, you could ask him a question about a class topic. Keep it broad, so he has many ways to answer. Don’t ask a question that can be answered with us or no.

Good luck.

Look them right in the eye, smile, and say “Hello!”
Find a way to bump into him and look startled, embarrassed, and say “Oh, excuse me! I’m such a klutz!”
If he’s sitting somewhere and the seat next to him is empty, go over and ask if that seat is taken. If he says “No,” sit down.
People like to talk about themselves, so ask him about him. Then tell him about yourself.
“Be bold! Daring!”

Current social environment is changed. That makes things more difficult.
You might start a zoom study group for whichever class you have together that is most demanding. Ask him if he would like to join, or even to help you get one started.
Most school friendships start in grade school, during recess. Seeing how various kids relate to each other makes the best path for choosing friends.
It gets more difficult in higher grades. That is what drives cruising, and infamous parties forward.
If a study group congeals, then at school contact can become more effortless. What’s more, it could improve grades for someone, or all.

Because you and he are in a class together, you have a perfect reason to start a conversation. You can approach him, introduce yourself, and ask a question about something recently said or discussed during the class.

As another idea, many guys wear sports merchandise—ballcaps, t-shirts, jackets, etc. with their teams’ logos. Sports comments are great icebreakers. “Did you watch Chris Sale’s return on Friday?:” “Finally, the Nationals broke their bad streak.”