To what extent, and how, does social background influence students’ attainment in higher education? Building on the life course perspective on educational inequalities, this PhD thesis focuses on patterns of inequality formation in French higher education and on an evaluation of educational policies to reduce them. It assesses the effect of social origin on pivotal outcomes of higher education careers in both the vertical dimension of stratification (access to higher education, dropout) and horizontal dimension (access and transfer to prestigious institutions). In order to provide a comprehensive assessment of patterns of inequalities, from initial access to final attainment, this thesis further combines the study of single key transitions with an analysis of whole students’ trajectories during their educational careers. Focusing on policy solutions, it estimates the effect of alternative pathways on the composition of the student body in prestigious institutions and provides a systematic review of the (quasi-) experimental literature evaluating the impacts of both outreach interventions and financial aid on the outcomes of disadvantaged students in higher education. Results first confirm the crucial role of previous education in shaping social inequalities in higher education outcomes. However, these results also provide evidence of a “lingering” effect of social origin in the French higher education system for some crucial outcomes, especially in the horizontal dimension of social stratification. They further confirm the relevance of the compensatory advantage hypothesis in the formation of social inequalities in higher education outcomes, as, in France, socially advantaged students with lower performance are better able to gain eligibility to higher education and to overcome failure in their first year of tertiary studies. Finally, the systematic literature review allows the conclusion that some late interventions, when well-designed, are efficient in increasing opportunities for disadvantaged students and reducing inequalities in higher education outcomes. Most notably, outreach interventions which complement information with personalized support are usually efficient in increasing access rates, and need-based grants appear to raise, often substantially, the graduation rates of disadvantaged students. Finally, the implications of these results for our understanding of social stratification in higher education and some promising avenues for future research are discussed.