The No Child Left Behind Act (NCLB) placed a new focus and accountability on the achievement levels of English learners by requiring that they develop English proficiency and meet the same academic standards that all children are expected to meet by year 2014. Administrators and teachers are looking at ways English learners might progress more quickly toward proficiency on state tests, both in English language skills and in other content areas. In some cases this means students have moved out of English language learner (ELL) programs after one or two years. Sometimes, it means incoming ELLs will bypass ELL programs altogether, entering classes alongside native English speakers, usually with some type of ELL teacher assistance. For ELL students who might otherwise get stuck on a separate academic track from their English-dominant peers, this sort of mainstreaming can be a good thing. Supporters of mainstreaming note that it can help students learn faster because they have English-proficient peers as models. And being included in all aspects of the school--rather than segregated into a separate classroom--can only help their sense of belonging. What's more, NCLB allows students to get credit toward graduation only for classes taught by "highly qualified" teachers endorsed in their subject areas. By moving students toward grade-level classes, teachers are helping them stay on track to graduate. Still, this very distinction has effectively reduced or eliminated many transitional subject-area classes taught by ELL-endorsed teachers. The effects of this trend can now be seen in middle and elementary schools, where students are often placed in grade-level classes with ELL teacher assistance but with little or no opportunities for students to be pulled out for specialized instruction. And rapid mainstreaming seems to ignore what research tells: It takes five to seven or more years for students to pick up the academic language needed to survive in grade-level classes. If English learners are to be mainstreamed into grade-level classrooms, one must look at the ways in which grade-level teachers can be taught basic second language acquisition theory and research. Teachers must be given the tools to incorporate effective and essential strategies and techniques into lessons so that English learners are not simply "sitting" alongside native English-speaking peers, but "learning" alongside them as well. In this article, the author describes the Sheltered Instruction Observation Protocol (SIOP), an effective tool for improving ELL student learning, which is used for the professional development of staff at Claremont Immersion Elementary School in Arlington, Virginia.