This study is a population-based investigation of children's school readiness with a national sample of low-income children, utilizing data from the Family and Children's Experiences Survey (FACES; 2000-2003). Guided by a developmental ecological framework, we posed 3 research questions: (a) How do children's early school readiness skills in the social and cognitive domains overlap (as they enter preschool)? (b) Do these configurations of school readiness skills meaningfully predict children's school adjustment by the end of kindergarten? (c) In addition to the patterns of children's school readiness identified at the beginning of their first Head Start year, do relevant family and classroom context factors help to predict and/or moderate end-of-kindergarten outcomes? Results revealed 5 distinct patterns of school readiness for this national sample of low-income children. These profiles related in meaningful ways to end-of-kindergarten outcomes, such that children in more competent preschool profiles did better over time. Moreover, these patterns of school readiness identified at the beginning of the Head Start year were the most consistent predictors of end-of-kindergarten performance, controlling for demographic and context factors. However, results revealed that proximal contextual influences in the family (i.e., maternal education and parenting style) and classroom (i.e., teacher experience, teacher education, and adult-child ratio) further predicted end of kindergarten performance across preacademic and social domains. Findings illuminated significant within-group patterns and variability among an at-risk population, relevant for informing early childhood education and early intervention. (Contains 4 tables and 3 footnotes.)