The school system is intended to offer all students the same opportunities, but most international surveys reveal an overall lower achievement for students from disadvantaged groups compared with more advantaged students. Recent experimental research in social psychology has demonstrated that schools as institutions contribute with their implicit cultural norms and structure to the production of inequalities. This chapter examines the role that a structural feature of school, namely meritocratic selection, plays in this reproduction of inequalities at school. First, we describe how meritocracy in the educational system can hold paradoxical effects by masking the virtuous/vicious cycles of opportunities created by educational institutions. Second, we present recent research suggesting that selection practices relying on a meritocratic principle—more than other practices—can lead to biased academic decisions hindering disadvantaged students. We propose that inequalities in school might not just result from isolated failures in an otherwise functional meritocratic system, but rather that merit-based selection itself contributes to the perpetuation of inequalities at school.