This dissertation studies college admissions in Brazil in the past two decades, a period characterized by a decline in the socioeconomic inequality in demand for higher education. The first chapter studies an affirmative action policy enacted at a flagship university in Brazil to lower the socioeconomic inequality in college access. I find substantial redistributive effects, particularly for first-generation and racial minorities. Low-income applicants also become more likely to apply to a selective major. However, some targeted applicants reach too high, missing their chance at acceptance. Such inefficiency is driven by a strict one-major-choice admissions design. Alternative mechanisms can improve efficiency while preserving the redistributive gains. Beyond college access, inclusion in high-earnings fields is an important channel by which affirmative action can promote social mobility. The second chapter studies the effects of temperature on performance in an exam used for college admissions in Brazil. It exploits a unique context in which this exam's stakes changed over time, induced by more universities adopting a centralized college admissions system. Results show that temperature during the exam negatively affects performance. However, as the exam stakes increase, students exert compensatory effort to counterbalance the adverse effects of temperature. These findings reinforce the role of investments in infrastructure to mitigate a source of inequality affecting exam performance and college access. The third chapter studies how affirmative action policies adopted by almost one hundred universities across Brazil changed high school persistence and demand for college. Most policies targeted applicants from public high schools, some of which included income and race criteria. Exploiting temporal and spatial variation in policy intensity, results show positive effects on high school persistence and demand for college among targeted students but negative effects for the non-targeted. These findings highlight the importance of affirmative action in shaping individual aspirations and, in turn, pre-college levels of education, demonstrating the far-reaching effects of affirmative action policies. [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://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]