Effects of Disruptive Peers in Endogenous Social Networks

This study uses sociometric data to show that social connections in the classroom shape the diffusion of the negative externalities on cognitive achievement generated by abused and neglected peers. We find the strongest negative effects for students who are socially closest to the abused and neglected peer. The fade-out rate of the negative externality is such that being three peers away from an abused and neglected peer is equivalent to having no such peers. Although the inverse effect-distance relation applies to both verbal and numeric ability, it is conferred through different mechanisms. The abused and neglected peer’s lower verbal ability harms her friends’ verbal ability, whereas it is the disruptiveness itself that harms classmates’ numeric ability.