New research confirms what parents have long suspected about the power of popularity in school: It makes kids more vulnerable to peer pressure.

A study in the journal Child Development placed 40 teens in an Internet chat room where they thought they were socializing with some of their popular and unpopular classmates. (In fact, they were receiving messages that had been programmed in advance by the researchers.) The teens agreed more often to take part in risky and aggressive behaviors, like smoking, drinking and fighting, when they believed that such actions were endorsed by their well-liked peers.

According to the study, parents and schools can improve teens’ behavior by changing the way kids view and react to peers.