Peer Heterogeneity, School Tracking and Students’ Performances: Evidence from PISA 2006

The empirical literature using large international students’ assessments tends to neglect the role of school composition variables in order not to incur in a misidentification of peer effects. However, this could lead to an error of higher logical type since the learning environment crucially depends on peer variables. In this paper, using PISA 2006, we show how peer heterogeneity is a key determinant of students’ attainments. Interestingly, the effect of peer variables differs depending on the country tracking policy: peer heterogeneity reduces efficiency in comprehensive systems whereas it has a non-linear impact in early-tracking ones. In turn, linear peer effects are larger in early-tracking systems. Results remain robust in both student- and school-level regressions and when we add school-level dummies and several controls correlated with the school choice to alleviate the selectivity bias