Abstract
Abstract This paper exploits random assignment of students to first-semester class groups at a leading Chilean university, combined with data on students’ secondary school backgrounds, to examine how exposure to former schoolmates shapes college success. The high concentration of secondary school peers within degree programs, together with random class group assignment, generates exogenous variation in exposure to familiar peers. While peer effects are theoretically ambiguous, our findings show that exposure to familiar peers in the first semester reduces first-year GPA by about 0.04 points (0.08 standard deviations). These effects appear to be driven by increased socialization opportunities that crowd out academic effort during the critical transition period to university life.