In this study, we explored the potential of two forms of discussion (disciplinary vs. traditional) for 39 sixth- and seventh-grade students with or at-risk for LD, before writing historical arguments. Nine teachers who led small group discussions in six heterogeneous social studies classrooms implemented the intervention. Students who were involved in disciplinary discussions (n = 19) scored statistically higher than their peers who engaged in traditional discussions (n = 20) on a measure of historical knowledge (partial eta-squared = 0.23), and wrote essays with better persuasive quality (partial eta-squared = 0.43) and greater evidence of historical thinking (partial eta-squared = 0.40). A delayed posttest delivered 8-weeks after instruction ended revealed that students in the experimental condition continued to write in more historically sophisticated ways than students in the comparison condition (partial eta-squared 0.19). Challenges, however, remain for struggling learners who must now meet both basic and advanced disciplinary literacy goals.