Educating dual language learners (DLLs) and English learners (ELs) effectively is a national challenge with consequences both for individuals and for American society. Despite their linguistic, cognitive, and social potential, many ELs--who account for more than 9 percent of enrollment in grades K-12 in U.S. schools--are struggling to meet the requirements for academic success, and their prospects for success in postsecondary education and in the...