This article describes the efforts of a U.S. History teacher to directly teach word meanings using the "robust vocabulary instruction" (RVI) approach, because research supports this method as a way to improve vocabulary knowledge for a range of students, including adolescents reading below grade level (i.e., struggling readers) and students with learning disabilities. Despite the important role that vocabulary knowledge plays in key student outcomes, many teachers allot minimal time (if any) to explicit instruction on word meanings. Explicit vocabulary instruction is necessary to improve students' academic achievement in diverse classrooms where many students are struggling readers whose word knowledge is especially limited. Taken together, the elements of the RVI approach provide a promising foundation for vocabulary instruction for struggling readers and students with disabilities. Using the modified approach to RVI outlined in this article, teachers in classrooms can improve word knowledge and access to academic texts for their diverse groups of students.