Teachers face the challenging job of differentiating instruction for the diverse needs of their students. This task is difficult enough with happy students who are eager to learn; unfortunately students often enter the classroom in a bad mood because of events that happened outside the classroom walls. These events--called setting events--can increase the prevalence of challenging behavior that disrupts the classroom. Teachers often feel overwhelmed when thinking about these problems, but when they begin to see the relation between setting events, antecedents, behaviors, and consequences, they can begin to address these issues in a proactive way that helps prevent the challenging behavior from occurring. The purpose of this article is to (a) describe the relationship between behavior and the environment, (b) highlight reasons that students engage in challenging behavior, and (c) provide suggestions on how to tackle these setting events in the classroom.