Suppose you are teaching a class of, say, 15 students. This is an intermediate level course in some subject. We'll say the course has a prerequisite called Course A. However it turns out that only 5 of your students demonstrate sufficient knowledge of course A; 66% of the students aren't up to par as defined by the requirements.

How do you reconcile this? Do you adjust the class to the new median? Or do you continue as planned and let those students struggle?