English language learners (ELLs) are the most rapidly growing student population in U.S. elementary and secondary schools, and this growth rate will continue throughout the next few decades. Indirect evidence has suggested that the youth population that grows the fastest has the highest risk of dropping out of school. This article reviews the literature on ELL students with a focus on the risk factors that characterize this expanding population. Limited English proficiency, disadvantageous socioeconomic status, and different cultural background are identified as the leading factors that influence ELL students' school outcomes. The authors discuss implications of these risk factors to teacher education and professional development in teaching ELL students. (Contains 1 note.)