Bullying is any form of psychological abuse, verbal or physical that occurs repeatedly among school children over time. Emotional bullying is most common, usually happening in classrooms and schoolyards. Victims are often children entering adolescence around 12-13 years old, with girls making up a slightly higher percentage. There are eight main types of bullying: social exclusion, harassment, manipulation, coercion, intimidation, aggression, threats, and social blocking, all seeking to isolate and marginalize the victim. Positive behaviors at school include being friendly with everyone regardless of differences and not socially isolating others.