From the abstract: "Practice and policy in early childhood education rely heavily on professional expertise and guidelines developed from research on early care and education (ECE) quality, but these guidelines have not been extensively researched. Data from six large studies of ECE quality were analyzed to relate structural and process quality indicators based on professional guidelines to children’s language, literacy, math, and social outcomes. Results indicated small gains related to some quality indicators (e.g., quality of teacher–child interactions, curriculum, and teacher and director education) for some of the preschoolers’ outcomes, but not other indicators (e.g., global quality, group size). Combining quality indicators into a single index also predicted gains in preschoolers’ language and literacy scores, but effect sizes for the quality rating were smaller than for individual indicators."