In urban middle schools, educators find it challenging to meet the literacy needs of the many struggling readers in their classrooms, including language-minority (LM) learners and students from low-income backgrounds. One strategy for improving these students' reading comprehension is to teach essential academic vocabulary in a meaningful, engaging, and systematic way. This article describes the development and evaluation of an academic vocabulary curriculum for sixth-grade mainstream classrooms with large numbers of LM learners who struggle with comprehension. In a study conducted in 21 sixth-grade classrooms, the curriculum was found to be effective both in improving students' vocabulary and reading comprehension and in supporting teachers' learning about how to teach academic vocabulary. Seven universal learnings for all classrooms are described and illustrated with specific examples of activities, perspectives from teachers, and insights from students, drawn from the study.