A peer group is both a social group and a primary group of people who have similar interests (homophily), age, background, or social status. The members of this group are likely to influence the person’s beliefs and behaviour. Peer groups contain hierarchies and distinct patterns of behavior. Eighteen-year-olds are not in a peer group with 14 year olds even though they may be in school together, just as teachers do not share students as a peer group.