Will Baude on the rudeness of his classmates:
I don’t mind when students slip into the back of a lecture hall late, but when the doors are in the front of the room and the teacher’s voice is easily overwhelmed, please have courtesy and remember that a late entry imposes costs on punctual students, and that 12(!) late entries in the course of a 50-minute class tempt me to resort to vigilante retaliation. If I’m ever an instructor, I will lock the doors to my classroom a few minutes after I start lecturing, to internalize the externalities.
When I was an instructor, I did precisely that.