There is limited research of observed writing instruction in inclusive, secondary diverse urban contexts. This study contributes to the field by investigating four urban secondary English teachers' perceptions of ideal writing instruction as compared with their actual instruction, which is primarily driven by high-stakes accountability measures. Sociocultural theories guide analyses of video-recorded writing lesson and interview data, with critical literacy theory framing the discussion and implications for teaching writing to diverse learners. Intersecting themes from interviews and observations point to constrained writing instruction and practices. Although the teachers recognized a responsibility to teach responsively to their diverse students' instructional writing needs, they are inhibited and unable to do so primarily because of high-stakes testing mandates that narrow the curriculum and limit teacher autonomy.