I think the fact that college students call the roll in class has almost been eliminated by society, because if college students really want to study now, they will come to the classroom early every day. He was already sitting in the classroom before the teacher called the roll, but even if some classmates came, his mind could not be in the classroom. He may be playing with his mobile phone or chatting with others, so I don't think roll call can directly affect whether a student studies hard or not, and it feels like a waste of time.