The purpose of this study is to examine the role of center-based care and children's school readiness in predicting their first and third grade reading and mathematics achievement. Predictions derived from an opportunity-propensity theoretical framework applied to data from the Early Childhood Longitudinal Study-Kindergarten Class of 1998-99. The study examined the impact of antecedent factors (e.g., socioeconomic status, parental expectations), opportunities to learn (e.g., center-based care), and children's propensities to learn (emergent reading and mathematics skills, approaches to learning) on first and third grade reading and mathematics assessment scores, and whether center-based care moderates the impact of multiple health and environmental risks for vulnerable children. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]