This article presents findings from a large-scale curriculum development, quasi-experimental study. Participating teachers implemented four U.S. history units in their diverse middle-grade classes; these units were developed to engage underachieving students in challenging history and democratic citizenship curriculum and instruction featuring discussion and inquiry. Initial results show that students in the treatment classrooms had significantly higher mean scores on a National Assessment of Educational Progress (NAEP)-based pre-post assessment than their peers in comparison classrooms.