Teachers Professional Development Cases in A Substitute Attached Elementary School were analyzed through the perspective of professional capital by focusing on organizations, members, tasks, and technologies through literature analysis and interviews. A school is rich in human capital because there are many teachers who are willing to develop professionality. The Grade group as teacher community creates social capital through communication, trust, and sharing. A school hasㄷbeen operated as an educational practice school for about 10 years, has created an environment where it can acquire decisional capital. This study showed that the practical operating system influenced the development of current teacher professionality. First the grade group as a teacher community became a venue to cultivate teachers human capital through cooperation, communication, and sharing as collective and social capital based on the accumulation of teachers human capital. And secondly, an environment is created in which teachers increasingly cultivate their professionalism for lessons and develop decisional capital by repeating reflective practice and reflection through open classes and lesson-sharing. Research results suggest that educational practice schools can be a teacher education model that results in both pre-service and in-service education, such as the Professional Development School(PDS).