I guess it depends. If you were at a large state-funded research university it would not surprise me for low-level and intro classes. When I attended a mid-si

I guess it depends. If you were at a large state-funded research university it would not surprise me for low-level and intro classes. When I attended a mid-sized elite university I only had this sort of experience with a few math and sciences courses that everyone in several different degree tracks had to take. My upper-level humanities courses, OTOH, were usually 8-20 students and always taught by a prof (and by the later years it was more likely for grad students to be taking the course than to be teaching it.) I guess that given the breadth of possible options when it comes to American universities this is one area where YMMV.