> He has conclusive evidence that at least 50 students cheated on the March midterm exam, making it the biggest known scandal at Brown and in the entire Ivy League
I'd like a citation for this being the "biggest known scandal" in the "entire Ivy League". Frequently such situations are kept somewhat quiet, for a variety of reasons. But fifty students is not a large number in courses that can enroll hundreds or up to a thousand students.
Ivy League classes usually aren't as large as their state school counterparts. At most you might get around a hundred students in a large lecture course; this is rare by design.
You can crunch the numbers on this to verify for yourself – most of these have a population of 6000 undergrads or so. 1/6 of all of the undergraduates need to take a single course for your "up to a thousand" to be true.
I agree that a citation would be nice, but the number of students is indeed large for Ivy League courses (as per the article, in this econ course, he had 86 students for a class that usually only has 30).
Harvard's larger courses enroll over 500 students. These are also introductory courses where you're most likely to see large cheating instances.