This mixed-methods study investigated the teachers’ perceptions of a yearlong Japanese Lesson Study professional development project on improving their teaching of Disciplinary Literacy. Analysis of the middle school teachers’ reflections, surveys, and interview data suggested that Lesson Study provided specific traits, such as unique strategies to collaborate, constant focus on student learning behaviors, specific ways to plan and observe how lesson plans are taught, and repetitive cycles, that differentiate it from other forms of Action Research. Through the thus defined features of Lesson Study as a very special form of Action Research, the data supports Study’ potential of becoming a sustainable, continual, context-based form of professional development for teachers while leading to local and/or statewide policy changes
