Social skills take practice. It might be outside your comfort zone but why don’t you start to seem more approachable. Try saying good morning to people as they pass by in the halls, class, or when they sit next to you. Make eye contact (most importantly remove any headphones and put up your down your phone). If they do start talking to you after that just talk about class or what they did or are planning to do this weekend. There are going to be awkward pauses as you try to figure what to talk about next and that okay. If you can’t further small talk you have initiated just tell them. “Well I have to go bye.” It’s small talk so it’s not a long conversation