Throughout the U.S., the academic achievement levels, high school completion rates, and college attendance rates of English-language learners remain markedly below that of their White, English-speaking peers. There is a growing and convincing body of research that high quality early childhood education can improve the educational achievement of children from diverse linguistic and cultural backgrounds and help to reduce this achievement gap before kindergarten. Therefore, it is important for the early childhood profession to have a clear understanding of how children acquire a second language in order to design high quality learning environments for children who are in the process of acquiring English as their second language.