This longitudinal study examined the extent to which the development of prosocial and aggressive peer norms was related to individual prosocial and aggressive behavior development across the first year of secondary education (three waves, n = 1,134 adolescents from 51 classes, M[subscript age] = 12.66). A distinction was made between descriptive norms (the aggregated average peer-perceived behavior within the classroom) and status norms (the within-classroom correlation between peer-perceived popularity and behavior). Results indicated that descriptive norms represented a stable, static peer ecology, whereas status norms were somewhat more dynamic and changed across the school year. The development of descriptive and status norms was associated with initial levels of individual prosocial and aggressive behavior, whereas the development of status norms was also associated with the development of prosocial behavior.