Currently, students from low-income backgrounds are underrepresented at selective colleges and universities in the U.S. With the introduction of many programs aimed at increasing the numbers of these students at selective institutions, it is important to understand how the characteristics of an institution can affect educational outcomes. Using restricted data from the "National Education Longitudinal Study of 1988" and the "National Longitudinal Survey of Freshmen," this paper finds that students from low-income families at more selective institutions achieve lower grade point averages than other students and are less likely to graduate within 6 years from their original institution. This effect seems to be mainly due to the gap between SAT scores of these students and the median SAT scores at the institution they attend. This paper also explores how these effects differ by race. Peer group size, as defined by income or race status seems not to affect grades or persistence, but does play a role in college major choice. These results can help educators and administrators to better understand the post-secondary experience of low-income and minority students, specifically at the more selective colleges and universities. (Contains 12 tables and 6 footnotes.)