The probability is just pow(0.5, N) where N is the student population, assuming that the distribution has no skew, assuming independence between students, and a

The probability is just pow(0.5, N) where N is the student population, assuming that the distribution has no skew, assuming independence between students, and assuming the students are drawn randomly from the general population. It's an exponentially decreasing function, so it becomes incredibly unlikely for large student bodies under these assumptions. I disagree with this argument, but that's the basis of it.