[egkjellman]

Because using previous tests is a common (and presumably ethical) method to study for previous exams.

As noted in the previous thread, it might have been a good idea for the students to have said "Hey, we've seen these questions before." But the professor using a bank of test questions changes the situation from "a bunch of students stole the test" to "the professor maybe should have used questions that people didn't have ready access to."