Comparing 14 developed countries, this chapter addresses two sets of research questions: (1) Is preschool attendance positively associated with reading competencies at later stages of children’s schooling experience? And to what degree does this positive association vary by the quality standards of preschool institutions and the weekly hours of attendance? (2) Do children from a disadvantaged social background benefit more from preschool attendance than children from more advantaged social origins? And is this more pronounced in countries with more favorable preschool characteristics? Analyzing two international cross-sectional datasets (PIRLS 2011 and PISA 2012), we find an overall positive link between preschool attendance and reading competencies at the level of primary and secondary school. In addition, this link is positively associated with the quality levels of preschool systems. Furthermore, our analyses point to a non-trivial ‘equalization effect’, i.e. children from a disadvantaged social background benefit more than do those from advantaged origins. But this only applies to countries with high-quality preschool systems.