The fastest-growing student population in U.S. schools today is children of immigrants, half of whom do not speak English fluently and are thus labeled English learners. Although the federal government requires school districts to provide services to English learners, it offers states no policies to follow in identifying, assessing, placing, or instructing them. Margarita Calderon, Robert Slavin, and Marta Sanchez identify the elements of effective instruction and review a variety of successful program models. During 2007-08, more than 5.3 million English learners made up 10.6 percent of the nation's K-12 public school enrollment. Wide and persistent achievement disparities between these English learners and English-proficient students show clearly, say the authors, that schools must address the language, literacy, and academic needs of English learners more effectively. Researchers have fiercely debated the merits of bilingual and English-only reading instruction. In elementary schools, English learners commonly receive thirty minutes of English as a Second Language (ESL) instruction but attend general education classes for the rest of the day, usually with teachers who are unprepared to teach them. Though English learners have strikingly diverse levels of skills, in high school they are typically lumped together, with one teacher to address their widely varying needs. These in-school factors contribute to the achievement disparities. Based on the studies presented here, Calderon, Slavin, and Sanchez assert that the quality of instruction is what matters most in educating English learners. They highlight comprehensive reform models, as well as individual components of these models: school structures and leadership; language and literacy instruction; integration of language, literacy, and content instruction in secondary schools; cooperative learning; professional development; parent and family support teams; tutoring; and monitoring implementation and outcomes. As larger numbers of English learners reach America's schools, K-12 general education teachers are discovering the need to learn how to teach these students. Schools must improve the skills of all educators through comprehensive professional development--an ambitious but necessary undertaking that requires appropriate funding. (Contains 2 figures and 93 endnotes.)