This paper examines peer effects in academic outcomes using data from Williams College. The author uses a quasi-experimental approach to measure the impact of first-year roommates' academic characteristics on students' grades. The study argues that first-year roommates are randomly assigned based on academic ability, allowing for a more accurate estimation of peer effects. The results show that peer effects are more strongly linked to verbal SAT scores than math scores. Students in the middle of the SAT distribution may perform worse if they share a room with a student in the bottom 15 percent of the verbal SAT distribution. Students in the top of the SAT distribution are least affected by their peers' SAT scores. The effects are not large but are statistically significant in many models. The study also considers the effects of broader academic environments and the influence of academic advisors. The findings suggest that peer effects are important in shaping academic outcomes, but the magnitude of these effects is relatively small. The study highlights the importance of random assignment in isolating peer effects and provides evidence that peer effects are more pronounced in verbal SAT scores than in math scores. The results have implications for understanding the role of peer effects in higher education and the importance of academic environments in shaping student outcomes.This paper examines peer effects in academic outcomes using data from Williams College. The author uses a quasi-experimental approach to measure the impact of first-year roommates' academic characteristics on students' grades. The study argues that first-year roommates are randomly assigned based on academic ability, allowing for a more accurate estimation of peer effects. The results show that peer effects are more strongly linked to verbal SAT scores than math scores. Students in the middle of the SAT distribution may perform worse if they share a room with a student in the bottom 15 percent of the verbal SAT distribution. Students in the top of the SAT distribution are least affected by their peers' SAT scores. The effects are not large but are statistically significant in many models. The study also considers the effects of broader academic environments and the influence of academic advisors. The findings suggest that peer effects are important in shaping academic outcomes, but the magnitude of these effects is relatively small. The study highlights the importance of random assignment in isolating peer effects and provides evidence that peer effects are more pronounced in verbal SAT scores than in math scores. The results have implications for understanding the role of peer effects in higher education and the importance of academic environments in shaping student outcomes.