The present study examined the relations between teacher-child interactions, teachers' Spanish use, classroom linguistic composition, and the school readiness skills of low-income, Latinx, Spanish-speaking dual language learners (DLLs), controlling for home and teacher background characteristics, with a national probability sample of Head Start children (i.e., from the Family and Child Experiences Survey [FACES, 2009]). Findings revealed that Head Start classrooms with higher concentrations of DLLs had teachers who reported lower average levels of children's cooperative behavior. In addition, DLL students in classrooms where teachers used more Spanish for instruction and demonstrated more emotionally supportive teacher-child interactions were found to have higher average scores on measures of approaches to learning. Implications and directions for future research related to classroom language contexts are discussed.