Aggression is defined as behavior that is aimed at harming or injuring others (Coie, Dodge, 1998). Challenging behavior isn’t always aggressive; sometimes it is disruptive or antisocial or annoying. But aggressive behavior is always challenging. It can be direct (hitting, pushing, biting, pinching, spitting) or it can indirect (teasing, bullying, ignoring). (Kaiser, Rasminsky, 2003).