This paper analyzes how the composition of an institution's student body affects performance of that institution's students, examining how average student quality and dispersion in student quality within the student body affects individual students' future earnings. The first section examines two reasons why one's peers would affect future labor market success: peer effects and employer screening. Peers can augment or detract from human capital accumulation through numerous types of interactions. Employer screening captures the role of one's fellow students in shaping the beliefs of employers about the quality of students at the institution. These may affect employers' actions in two ways (the level of student quality may affect the intensity by which employers recruit, and the dispersion in student quality may affect the degree to which employers screen by ability when interviewing students). The paper reviews relevant research, then uses 1982 High School and Beyond Survey data to provide additional evidence. Findings are consistent with previous research. Overall, level of student quality at an institution is an important determinant of earnings. A 100-point increase in the median SAT relates to a 3-percent increase in student annual earnings. Students with lower SAT scores appear to receive the highest premium from attending an institution with a high median SAT. (Contains 21 references.) (SM)