摘要：The study aims to 1) identify the teachers’ problem to develop a development model of professional teachers with a lesson study-based approach at Muhammadiyah Schools of Sukoharjo regency, 2) find an effective lesson study model as a development model of professional teachers, and 3) analyze a lesson study validation as a development model of professional teachers. The research used a phenomenology descriptive-qualitative method. The subjects included the students, teachers, principals, department head of education, and members of the Regional House of Representatives. The techniques of the data gathering employed the observation, documentation, and in-depth interview. The technique of the data analysis applied the first order understanding and second order understanding. It could be concluded that the four problems to improve the teachers’ professionalism with a lesson study-based model are as follows: 1) internal, 2) external (teachers’ commitment and concern), 3) an effective lesson study model based on a plan-do-see circle, collaboration, and collegial tutor, and 4) a lesson study validation in relation with the validations of open lesson and reflection, theory, and implementation.
