This brief presents research findings as well as policy recommendations arising from a study of the No Child Left Behind Act and its implications for immigrant children and English language learners (ELLs). Analyses are based on nationally-representative data from the Schools and Staffing Survey and detailed case studies of selected elementary schools and school districts serving high concentrations of ELL students. Results reveal an extraordinary degree of concentration of ELL students in a few schools that tend to be large, urban and serve a predominantly minority student population. Case studies at some of these schools suggest that, while implementation of NCLB has resulted in problems associated with increased testing (exacerbated by the use of inappropriate tests), the law has also had a positive effect on the education of ELL students as it has increased the attention paid to these students; fostered the alignment of curriculum, instruction and professional development; and raised the bar for student achievement. Implications of findings for the education of ELL students, particularly in schools serving low concentrations of English language learners, are discussed. Policy recommendations presented include the development of appropriate tests for ELLs, the inclusion of pre-K in NCLB legislation, and the provision of professional development for teachers.