“…The presence of such negative spillover effects adds a social cost of an individual's early childhood illness, which so far has generally been ignored by most policymakers and researchers. This paper is also broadly related to the literature on peer compositional effects, which study the effects of peers' gender 11,36,40,49,52,67 ; ability 16,25,53,68,98 ; migration status 41 ; parental characteristics 10,17,18,63,100 ; and smoking 58,61,62 . The paper is also closely related to the literature examining the effect of peers' behavioral or mental di culties on students' academic achievements 1,50 .…”