An 18-year-old senior in high school walks into the classroom with a hood pulled over his eyes, his ear buds screaming heavy metal music, carrying no textbooks, and acknowledging no one in the classroom. The teacher speaks up and says, “What's up, Andy?” Andy picks up a binder that was left in the classroom the previous day and before he walks out of the class quietly says, “The ceiling.” Is this an example of defiant behavior or would it be considered a form of disruptive behavior? Or is this just Andy's way of saying hello?