There is a virtual consensus regarding the types of language processes, interactions, and material supports that are central for young children to become proficient readers and writers (Shanahan et al., 2008). In this study, we examine these supports in both home and school contexts during children's critical transitional kindergarten year. Participants were 70 children living in 2 different communities: neighborhoods of concentrated poverty (i.e., poverty rates over 40%) and borderline neighborhoods (i.e., poverty rates of 20-40%). From an ecological perspective, our goal was to examine the quantity and quality of knowledge-building supports in these contexts, and their relationship to children's school readiness outcomes. Interactive parent-child tasks were designed to elicit child-directed language in the home, while naturalistic observations in the kindergarten classrooms captured teachers' child-directed language. Children living in concentrated poverty were more likely to experience language of more limited complexity and diversity in both home and kindergarten contexts as compared to children living in borderline communities. We argue that the "double dose of disadvantage" in the language supports children receive at home and at school may affect their school readiness in significant, yet distinct, ways.