Thesis: This thesis is composed of three independent essays studying the role of the schooling and social environment in which individuals make their educational, work or family decisions. The first chapter studies the impact of enrollment at a more selective Parisian high school on students' performance and choice of field of study. We compare students' educational outcomes depending on whether their 9th grade standardized score fell just above or below an admission threshold, and we find that enrollment at a more selective high school has no impact on students' performance but induces female students to turn away from scientific fields and settle for less competitive ones. Our results are consistent with lab-experiment findings on gender differences in attitude towards competition and bad grades. The second chapter analyzes grade repetition in higher education and focuses on the spillover effects induced by grade repeaters on undergraduate freshmen. We distinguish between spillovers effects induced by higher- or lower- achieving repeaters to disentangle class size from composition effects, and we find that grade repetition generates little congestion effects but has important negative composition effects. We show that the performances of freshmen are very sensitive to the number of higher-achieving repeaters while they are not impacted by the number of lower-achieving repeaters. One potential mechanism would be distortion in teaching practices. The last chapter studies the impact of temporary contracts and youth unemployment to explain observed delays in age at first cohabiting relationship and in age at first child. Using French data on the work and family history of large samples of young adults, this chapter provides evidence that access to permanent jobs has a much stronger impact than access to temporary jobs for family formation. According to our estimates, about 25% of the increase in age at first cohabitation and about 40% of the increase in age at first child observed during the second half of the century can be explained by the rise in unemployment and in the share of temporary jobs among young workers.