Negative reinforcement strengthens a behavior by removing an aversive or opposing stimulus; punishment is designed to decrease or suppress a behavior. For example, if the teacher says, "When you are quiet, you may go to recess," the behavior that the teacher is trying to reinforce is for the class to be quiet. So, the class must quiet down before they are rewarded with going to recess. With punishment, however there is no opportunity to escape the situation and go to recess. In a punishment situation, the teacher might say, "Because you have not quieted down, you may not go to recess." The teacher is trying to suppress the children's noisy behavior.