I have in my syllabus and “Rules of Engagement” brief a clear statement that on-time arrivals are expected and regular late arrivals result in points taken away from assignments.
I also started to lock the door to the room. The sound of the handle turning and then the sound of a body bumping into the door with the subsequent knocking is funny. Once the door is locked, it is locked. You are late—you lose. Thing is, students that make an effort to arrive on time support locking the lazy out of the room.
This was a state college which "socially promotes" a lot of racial minorities. I tutored on-campus for some extra money and encountered black college students who couldn't do simple arithmetic!!!