That would make the teacher completely unavailable for grading assignments, answering student questions outside of class, or much of anything beyond simply speaking to students. Someone needs to read all those history essay questions on the test, and then change something when most students get something wrong.

A 50+ person class would similarly limit students from asking questions. At which point you might as well just show videos. Some introductory classes are taught in huge auditorium’s but they still require additional TA’s and don’t work for upper level classes.

Don’t get me wrong, you could simply have an online system with canned videos, multiple choice question tests, and zero ability to ask questions. But, that’s not a collage education.