Nearly all high school seniors plan college, but many low-income students do not enroll. Moreover, among students who do enroll, low-income students often pursue less dependable college pathways. While research typically focuses on college cost and academic preparation as explanations of socioeconomic differences in enrollment outcomes, other barriers are often overlooked, and some may be more easily reduced. Complex, unstated, and unpredictable admissions and financial aid procedures frustrate many families, but for low-income students, these can serve as barriers to college enrollment. Using quantitative data from all seniors in Chicago Public Schools (CPS) and interviews with students and counselors, this dissertation seeks to understand whether and how high schools may reduce gaps in the college enrollment process. The first study examines how a new advising model in CPS, the college coach program, potentially improves college enrollment outcomes. Results suggest that coaches use new college advising strategies to create college-related social capital that helps students to complete key college actions. The second study uses a difference-in-differences design to analyze the effectiveness of the coach program. Results suggest that coaches improve some college enrollment outcomes and do so by increasing the number of students completing college actions. Moreover, unlike many educational reforms that contribute to a process of cumulative advantage, coaches appear to benefit the least advantaged students. The third study is a descriptive study that details an understudied dimension of college enrollment, part- versus full-time enrollment, using a different group of students than previous studies, refined definitions of "part-time," a new kind of predictor (high school histories), and considering variation across subgroups. Like previous research, this study finds a negative relationship between part-time enrollment and persistence in general, but not for all definitions of part-time or all groups of students. Moreover, this study finds that students' high school histories predict their enrollment intensity and college persistence suggesting that traditional college persistence models, which assume that persistence relates only to college experiences, may be incomplete. With national policy deeply committed to improving college outcomes, this dissertation may contribute to a better understanding of various policy approaches, their mediating processes and outcomes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]