Two recurring findings at the intersection of social stratification and education research are (1) on the hopeful side, the power of a postsecondary education to dampen the influence of socioeconomic origins on socioeconomic destinations, and (2) the less sanguine finding that postsecondary participation and completion are distributed with massive inequality across socioeconomic origins. With the goal of finding ways to ameliorate this inequality, this dissertation comprises three studies that draw on substantive literature in social stratification and methodological literature in causal inference and effect heterogeneity. Each study assesses whether one idea for how to narrow socioeconomic inequality in postsecondary education holds up against empirical scrutiny. Chapter 2 Précis Studies in social stratification have used siblings as a tool to learn about the intergenerational transmission of advantage but less often have asked how siblings impact one another's life chances. I draw on social capital theory and hypothesize that, when youths attend college, they increase the probability that their siblings attend college. I further hypothesize that this effect is strongest among youths whose parents do not have college degrees. Findings from a U.S. national probability sample support both hypotheses. While it is possible that confounding factors drive the estimates, I conduct robustness checks that show confounding would need to be very atypically strong to invalidate a causal interpretation. The positive main effect suggests that an intragenerational transmission of educational advantage exists alongside the intergenerational transmission that receives more attention. Effect heterogeneity points to the potential redundancy of college-educated siblings' benefits when youths already receive similar benefits from college-educated parents. Chapter 3 Précis In 2015, Wisconsin began mandating that all 11th-grade students in public high schools take the ACT college entrance exam and the WorkKeys career readiness assessment. With a series of quasi-experimental analyses, we evaluate this policy. Applying an interrupted time series analysis, we estimate heterogeneous effects of the policy on four-year college attendance with joint respect to economic disadvantage status and propensity to take the ACT in the absence of the policy. We find that the policy has boosted four-year college attendance among economically disadvantaged students with middling propensities to take the ACT and among economically advantaged students with high propensities. Overall, the evidence suggests that the policy induced more economically advantaged students than economically disadvantaged students to attend a four-year college. A regression discontinuity design fails to find evidence that being deemed career-ready by one's WorkKeys scores affects one's probability of four-year college attendance, casting some doubt that the WorkKeys component of the policy played a significant role in the impacts of the policy on college attendance. The results tentatively suggest that students update their college attendance behavior based on new information about their college readiness but not based on new information about the immediate returns to forgoing college. Accordingly, the results lend qualified support to Bayesian learning theory. Chapter 4 Précis According to the theory of Effectively Maintained Inequality (EMI), children of economically advantaged parents not only enter each level of (post)secondary education at higher rates than do their less advantaged peers, but also enjoy educational opportunities at each level that position them more favorably to continue to the next level. Governments may play a role in facilitating or limiting EMI because they allocate appropriations to public universities; the more between-university variability in these funds, the more horizontal differences high-income students may exploit. I ask whether Wisconsin's unequal pattern of appropriations across its institutions of higher education exacerbates income-based disparities in college persistence. I test two hypotheses: (1) Economically advantaged students sort into the universities with greatest appropriations; (2) Appropriations promote first-to-second-year persistence. Evidence in favor of both hypotheses would support the claim that an unequal allocation of appropriations exacerbates college persistence disparities and, accordingly, suggest that unequal allocation facilitates EMI. Results support the first but not the second hypothesis. I then attempt to explain why appropriation appear to be independent of first-to-second-year persistence by examining whether changes in state appropriations were associated with changes in university expenditures that promote persistence. I find that academic support expenditures are most important for persistence in Wisconsin and that increases in state appropriations are not associated with increases in these expenditures. Taken together, the results do not present evidence that the Wisconsin state government can easily facilitate or limit EMI based on its allocation of state appropriations to universities.