First, let me say that now that I have read Simpson a little more, I have found some answers. As librarians, none of us wants the unpleasant job of being the "copyright police." The two agencies responsible for enforcing copyright law are the FBI and the Justice Department. But it's not like the FBI are going to come bursting into your school with guns and dogs because an English teacher makes 30 copies of a simile worksheet every year.
So how exactly do people get caught? One way is that they get turned in by someone - perhaps a disgruntled student. Or maybe an angry employee turns the district in for something. More interestingly, some sales reps are required to report any copyright infringement they see. And how many times do we see publishing company reps in the library or texbook companies in the schools? And believe it or not, also according to Simpson, there is such a thing as a "bounty hunter" who collects rewards for turning in copyright infringers.
Who knew? I certainly didn't!