In addition to reviewing the existing literature, we add to it by using longitudinal data from a large-scale microsimulation model to look at current gaps in school readiness by family income, race and ethnicity, and gender. We then show how those school readiness gaps reverberate throughout a child’s educational career, leading to disparate outcomes later in life, and providing some insight into the mechanisms that explain why early interventions may have long-term effects. (author abstract)