The education pipeline is characterized by a series of well-defined and extensively documented transitions. From preschool to kindergarten, elementary to middle to high school, and college to work, students at multiple stages of human development experience transitions that shape their downstream outcomes. In this dissertation, I use administrative data and quasi-experimental analytic approaches to examine how people, programs, and policies impact individual outcomes during periods of educational transition. In my first essay, my co-author and I examine how exposure to peers on the school bus influences one's own academic achievement and behavior. We draw from an established literature on peer effects and an emerging literature on neighborhood effects to show that an out-of-school setting like the school bus can meaningfully impact individual performance. By focusing on idiosyncratic changes to the sets of students riding the bus together that result from school transitions and the spatial structure of bus routes, we develop an approach to estimating peer effects that takes advantage of transition data. To estimate bus peer effects, we measure the extent to which changes in the unexplained component of the performance of a student's bus peers predict otherwise unexplained changes in that student's own performance. We estimate our model using a leave-out-student strategy where we measure the effects of bus peers for each student using data only from their peers. Our identifying assumption is that conditional on student, school-by-school-pair, year, and grade fixed-effects, variation in the residual of student performance common to students who ride the bus together is unrelated to factors apart from their bus ride. We report two main sets of results. First, we show that a standard deviation (SD) shift in bus peers' academic performance corresponds to own changes of 0.02 SD from elementary to middle school and 0.05 SD from middle to high school. We also document shifts in behavior ranging from 0.05 SD from elementary to middle school to 0.08 SD from middle to high school. These results demonstrate that out-of-classroom interactions are more meaningful in adolescence and are roughly half the magnitude of comparably estimated school, counselor, and teacher effects. Second, we leverage survey and neighborhood data to show that the effects of social interactions on the school bus are only partly related to students' prior academic performance and that there is little evidence that bus effects are related to survey-based measures of school climate or student engagement. Our results show that social interactions in informal settings may be important in shaping student learning outcomes, highlighting the need for research to better account for the various out-of-school settings in which students participate. In my second essay, I move along the education pipeline to high school, where students grapple with questions related to the transition to college and the workforce. In my high school setting, I examine how access to and attainment of industry-recognized certifications (IRCs) shapes post-high school intentions, postsecondary enrollment, and earnings. IRCs are developed by industry groups or corporations for students hoping to demonstrate preparedness for a particular job or sector. In my sample, I leverage proprietary IRC data that covers a diverse set of industry areas, including business, the arts, and manufacturing. In my setting, students sit for an IRC exam and earn the certification if they obtain a passing score. If IRCs represent a postsecondary signal, then certified students may express interest in four-year college or experience higher enrollment rates. If they represent a workforce signal, then certified students may have higher earnings. I use two analytic approaches to describe the effects of earning an IRC in high school. First, I use matched samples of certified and non-certified students to show that IRC earners are considerably more likely to plan to and actually enroll in a four-year college. Moreover, these same students are considerably less likely to plan to and actually enroll in a two-year college. This result suggests that there is a trade-off on the margin of college type. Second, I leverage arguably exogenous assignment to certification status at the passing threshold to show that an IRC does not impact outcomes for the marginal examinee. At best, I uncover suggestive evidence that the marginal IRC earner is slightly more likely to express an interest to work after high school and delay college enrollment. This joint finding suggests that the marginal earner, in contrast with the average earner, uses IRCs as a workforce signal. I find no evidence through either approach that IRC attainment shapes short-term quarterly earnings. The results suggest that for the average certified student, IRCs constitute a component of the college-readiness portfolio while for the marginal student, IRCs weakly signal intentions to work. In all, the results show that IRC effects are more muted than credential proponents may suggest. Finally, in my third essay, my colleagues and I examine the effects of credential stacking that occurs during transitions between college and work. Credential stacking refers to the practice of earning multiple credentials within a fixed period of time. The vast majority of research estimating returns to credentials focuses on the single degree--whether the associate's, bachelor's, master's, or professional degree. Credential stacking has emerged alongside the demands of employers for workers who can re-skill or up-skill in the face of technological change, the pandemic economy, and demographic shifts. To measure the effects of credential stacking, we leverage statewide administrative data in a state that has emphasized stacking as a strategic workforce initiative. Using decades of postsecondary and labor market data, we use fixed effects approaches with individual time trends to show that credential stackers earn roughly $800 more per quarter than their counterparts who attempt to stack but ultimately do not. Moreover, we show that the benefits of stacking accrue largely to female and non-white stackers, suggesting that credential stacking may be a viable approach to skill development that addresses persistent equity gaps. We also show that credential stackers who pursue a second associate's degree (whether from a certificate or first associate's degree) earn more than stacking by other means, and that stackers in healthcare fields earn roughly twice as much per quarter as the average stacker. Our results suggest that states and institutions continue to pilot and evaluate credential stacking pathways as they pursue approaches to creating broad economic opportunity for adult learners. Taken together, these three empirical studies shed light on factors that shape individual trajectories at critical inflection points. Each paper contributes to an established research paradigm in important ways. New estimates of transition-induced bus peer effects that approach the lower bound of established effects in education (e.g., teacher, leader, or school) suggest that out-of-school contexts matter. Causal effects of IRC attainment on college enrollment and quarterly earnings paint a mixed picture and suggest that claims about the promise of certification for school-to-work transitions may be exaggerated. Finally, returns to credential stacking in the transition between school and work suggest that the practice boosts average earnings and can reduce longstanding equity gaps in the process. [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/en-US/products/dissertations/individuals.shtml.]