Research Findings: An observational study of 60 Head Start teachers and 341 children (177 boys, 164 girls) enrolled in their classrooms found teachers' book-reading practices to predict growth in children's receptive vocabulary. Multilevel growth analyses indicated that children in classrooms where teachers used more book-focused utterances made greater gains in receptive vocabulary (PPVT-III) across the preschool year, particularly when children entered Head Start with lower receptive vocabulary skills. Practice or Policy: The study identified teachers' book-reading practices as an indirect pathway between teachers' education and children's language growth across preschool. Teachers with more years of formal education and professional training in early childhood used more book-focused utterances. Teachers' education was not directly related to growth in children's receptive vocabulary across preschool. (Contains 1 figure and 6 tables.)