This article begins with a review of the forms of writing promoted in the Common Core State Standards. Across content areas, Common Core encourages teachers to attune students' writing to rhetorical concerns of audience, purpose, task, and disciplinary thinking. To address these concerns, teachers might take a rhetorical approach to the study of genres. In this view, genres are seen as resources writers use to build and act in particular situations. That is, genres help writers shape their writing to fit particular audiences, purposes, tasks, and forms of disciplinary thought. This article explains the rhetorical approach to genre studies by describing how particular genres (e.g. lab reports) are used by people to negotiate particular situations (e.g. labs in chemistry classes). Examples are offered throughout the article of how genre studies can be carried out in classrooms.