The purpose of this study was to explore teachers’ beliefs as practical knowledge in order to examine various aspects of Korean language classes. For this purpose, I examined a high school sophomore Korean language class conducted by a teacher(not disclosed) for one semester and I analyzed the teacher’s beliefs as noted in the context of the class. To understand the overall structure of the Korean language class, I analyzed the collected discourse materials and conducted in-depth interviews with teacher and students. The teacher had a personal belief system of “critical perception of social injustice,” along with goals and visions for an ideal Korean class as a “Korean language class for life.” This belief system included their conviction that reading allows students to “read the world,” and conveyed a diverse range of explicit and implicit belief as revealed through the use in the class of various methods that sometimes came into conflict. The teacher’s belief system contributed to the dynamic construction of their practical knowledge in special situational and social contexts, thereby constituting a crucial pillar of their professional expertise.