Understandings about genre govern nearly all of the choices writers make. They make choices about form, persuasive moves, conventions, and even ideas through a sense, whether articulated or tacit, of the social situation from which a piece of writing is arising. In a semester-long high school writing course, the authors engaged students in a series of activities designed to help them develop genre awareness. The goal was to support students in becoming more independent and flexible writers who possess genre analysis skills they can apply anywhere. Through whole-class genre studies, self-selected genre studies, and collaborative analyses of state test materials, students built deeper understandings about genre. Their sense of what is "OK" in a piece of writing shifted from successful evaluation by a teacher to successful navigation of the demands of a given rhetorical situation.