High-quality early care and education (ECE) programs are thought to increase opportunities for all children to succeed in school, but recent findings call into question whether these programs affect children as anticipated. In this article, I examine research relating the quality of ECE to children's outcomes, finding somewhat inconsistent and modest associations with widely used measures of process and structural quality, and more consistent and stronger associations with other dimensions of ECE such as curricula and type of ECE program. I discuss why the associations between ECE quality and outcomes are so modest, including limited children's outcomes, psychometric issues with quality measures, and a need to revise and expand measures of ECE quality. The evidence indicates that we need to focus on the content of instruction and teaching practices, as well as the extent to which teachers actively scaffold learning opportunities. We also need to continue to focus on the quality of interactions between teachers and children, and on children's access to age-appropriate activities. (author abstract)