It's taken as conventional wisdom that larger class sizes are a bad idea, whether we talking about kindergarten or college calculus. I sometimes wonder how big a determinant of student learning class size really is though. Place a large number of highly motivated and talented students in a classroom with a motivated and talented instructor and plenty of learning will happen. And I think we can agree that there's a certain limit to the number of students that can be in a room and still achieve a friendly or collegial enough atmosphere for serious discussion. But I wonder how far this goes. Is 100 worse than 50, in a philosophy lecture class, say? Is 300 worse than 100?
But the real problem with large class sizes is, of course, us. And by that I mean that large classes mean more of the most demanding and time-intensive, but often least rewarding, work of teaching: grading, etc. Large class sizes ultimately make for tired teachers, and tired teachers are not especially motivated or energetic. This of course is a hard argument to push in any real life context, since it suggests that we instructors have limits and are not superhuman.
Yet the question still strikes me as a good one: To what extent is class size an impediment to learning, especially in philosophy?