Although the movie takes place at an "Ivy League" college, it was in fact shot entirely in Northern Arizona, mostly at Northern Arizona University in Flagstaff in the fall of 1976. I was involved in the theater department there, and most of the extras in the film are then-members of the theater department.
There is an absolutely ludicrous scene in this film (if you know your Arizona geography) that shows several cast members riding bikes from the college to a creek. We NAU'ers know that the campus and said creek (Actually Oak Creek Canyon) are about 35 miles apart, and while the trip there is all downhill, it would be literally IMPOSSIBLE to ride a bike back UP that same road!