Teachers always have an ace up their sleeves, the ultimate threat to make students shut up and pay attention. “You know we write a class test soon, so maybe you should listen, if you don’t want to fail!” It often works, even the worst students at least pretend to listen now because they know they ought to. Sometimes “good” students remind others of the impending class tests, to get them to their senses, unable to understand how you can’t take it more seriously. The more effective tactic is to just threaten with a surprise test to keep everyone in check. If that makes teaching sound like training dogs not to bite, then that’s what some teachers make it sound like. And class tests and tests, written examinations in general, are the standard methods of authority in school, accepted and expected.