Traditional literacy instruction is perhaps still necessary but is certainly no longer sufficient to prepare learners for participation in the range of literacy practices that characterize an increasingly participatory culture. This article identifies discrepancies between traditional instructional practices that emphasize individual mastery of abstract concepts and skills and new media literacy practices that rely upon collaborative, social, and context-specific activity. In particular, mainstream assessment practices become problematic for teachers who are interested in integrating these so-called "participatory practices" into their classrooms. Through a description of a year-long collaboration around a secondary language arts curriculum, we present an assessment framework designed to support a social model of learning and to help prepare learners for engagement with and participation in a range of knowledge-building and problem-solving activities and communities, while supporting gains in more traditional curricular and standards-based assessments. This framework, which we call "participatory assessment," builds on previous work in science and math instruction, as well as in immersive video games, and extends that work into the secondary English language arts classroom. This article describes the curriculum, the approach, and some of the assessment design principles that emerged. (Contains 3 footnotes and 1 table.)