This study compares classroom quality and improvements in children’s language skills for programs implementing two Head Start classroom language models: (1) dual language model and (2) English with home language support (EHLS). The dual language model allocates time for teaching only in Spanish and for teaching only in English. In the EHLS model, teaching is mainly in English, but various approaches are used to support home languages (e.g., translation, labeling). Specifically, I conducted analyses to examine the following research questions: 1. Are there significant differences in quality ratings between classrooms using the Head Start dual language model and classrooms using the Head Start EHLS model? 2. Are there significant gains in children's language development in English and Spanish from the beginning of the school year to the end? Do those gains differ for classrooms using the dual language model compared with classrooms using the EHLS model? 3. How does classroom quality relate to gains in children's language development and classroom language model? Recruitment for the sample occurred in 153 Head Start and Migrant Head Start classrooms in southern and central California and in southern Florida. (author abstract)