OBJECTIVE: Together with family factors, early care and education (ECE) services were shown to improve school readiness in kindergarten. However, it is not clear whether better school readiness at age 6 years translates into higher rates of high school graduation years later. Our objective was therefore to investigate the long-term associations between the use of ECE and high school graduation while considering the sex of the child and the socioeconomic status of the parents as moderators. METHODS: Participants were children from the Quebec Longitudinal Study on Child Development (QLSCD) born in 1997 to 1998 (N = 2001). Intensity and type of ECE exposure were measured from age 5 months to 5 years. Administrative records were used to determine whether students had obtained a high school diploma by age 20 years. Factors explaining differences in the profiles of ECE users were controlled using propensity score weights. RESULTS: Twenty-two percent of students did not have a high school diploma by age 20 years. Compared with children never exposed to center-based care, those exposed early (i.e., before toddlerhood) had better odds of graduating from high school (odds ratio = 1.49) after controlling for confounding factors. Late exposure to center-based care was not related to high school graduation rates. CONCLUSION: Exposure to regulated and center-based ECE on a regular basis from toddlerhood to school entry was associated with higher rates of high school graduation. Regulated center-based ECE at the population level may improve rates of high school graduation.