Bullying is intentional aggressive behavior. It can take the form of physical or verbal harassment and involves an imbalance of power (a group of children can gang up on a victim or someone who is physically bigger or more aggressive can intimidate someone else, for instance).
Bullying behavior can include teasing, insulting someone (particularly about their weight or height, race, sexuality, religion or other personal traits), shoving, hitting, excluding someone, or gossiping about someone.
Bullying can cause a victim to feel upset, afraid, ashamed, embarrassed, and anxious about going to school. It can involve children of any age, including younger elementary grade-schoolers and even kindergarteners. Bullying behavior is frequently repeated unless there is intervention.