If “Bad Santa,” uh…excuse me, “Bad Teacher,” is on your must-see list, it’s probably because you’re curious to watch Cameron Diaz as an unapologetically rude teacher. Don’t feel ashamed though.

Your interest is logical, since there’s serious comedic potential whenever an actor breaks away from normal type casting. It can be risky if the actor flops, though it can be a real treat if he or she successfully plays a new type of role. At first, “Bad Teacher” rewards you for taking the plunge, by creating laughs with some subtle humor and great editing.

You’re initially introduced to the te...