This study examines the teaching practices of three groups of co-teachers, six individuals co-teaching in English language classrooms in public elementary schools in Gyeonggi province in South Korea. The ways in which each of the teachers perceived their educational and professional histories as impacting their co-teaching was also investigated with particular attention to how the co-teachers negotiated the co-construction of their identities both within and outside of the classroom context. This critical qualitative study used positioning theory (Davies & Harre, 1990) to investigate the ways the teachers positioned themselves, one another and how they were positioned by others as well as the effects on their teaching practices and identity constructions. Data were collected through individual and partnered interviews, classroom observations, and audio recorded co-planning sessions. The results of this study indicate the teachers each had come to accept individualized classroom roles, and had simultaneously negotiated to embrace complementary roles and responsibilities with their co-teachers. The study found the teachers' lived experiences, both educational and professional histories, played key roles in shaping each teacher's teaching philosophies and practices. Complex layers and hierarchies of ownership of English and its teaching emerged, as did the necessity to look beyond perceived linguistic competencies as being the single identifying factor in identity construction, and to embrace more of teacher's multifaceted identities. Additionally, it appears that based on current co-teaching practices, a de-professionalization of English teachers in Korea is emerging. This study's findings offer implications for teacher identity, future public policy drafts on co-teaching in Korea, as well as insight on co-teacher development training programs for teachers in Korea. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]