This project develops assessment items and tasks to appraise content knowledge of teaching in secondary English language arts (ELA), focused on the sorts of understanding and skill needed to teach secondary school ELA. A core responsibility of teaching is helping students develop understanding and skill in academic content. Content knowledge for teaching (CKT) (Ball, Thames, and Phelps, 2008) involves being able to unpack proficient knowledge in ways that make it explicit. The specialized ways of knowing needed for teaching are not intuitive and are often at odds with the “obviousness” that accompanies fluent expertise. This project is investigating ways to appraise teachers’ skills at making the tacit explicit and understandable inside the content and practices entailed in secondary ELA teaching.