In order to determine whether classmates' prosocial behavior is related to lower anti-social behavior of students, Verena Hofmann and Christoph Michael Müller conducted a longitudinal study among lower secondary school students in Switzerland (mean age = 13.8 years). The sample included 55 classrooms in eight schools, and the researchers analyzed data collected at the end of Grade 7, Grade 8, and Grade 9. Participants completed self-reported assessments on prosocial behavior, anti-social behavior, and anti-social attitudes. Classmates' pro- and anti-social behavior for each student was calculated by averaging all students' scores in a class, excluding the students' own score.