Friendship network in the classroom: Parents bias on peer effects

•For 452 students divided in 33 classes in six schools in the district of Treviso (Italy), we interviewed both parents and children.•We find that the parents’ network has a bias: parents expect peer effects on school achievement to be stronger than what they really are.•Thus, parents of low-performing students report their children to be friends of high-performing students.•Policy implication 1: when looking for peer effects, tracking the network this bias must be taken into account.•Policy implication 2: lack of parental knowledge is bad per se, and has been related to low school performance and school drop outs.