This thesis presents an examination of the beliefs that non-native English speaker teachers had about using the first language (L1) and target language (TL) when teaching English, and how these beliefs influenced the social construction of the language classroom. The central idea for the thesis arose during the author’s time as a teacher trainer in South Korea. During this time, it was noticed that despite government mandates supporting an English only approach to English learning, teachers were still reluctant to exclude their L1 completely. To investigate why teachers were resisting government mandates, beliefs were explored via a two-step series of interviews which separated the development of beliefs into discrete stages to reveal the different influences acting on the formation of these beliefs. The stages were divided into initial assumptions about language use, tentative attitudes, and then firmer beliefs. Important influences that acted upon the participants included the language use of their own language teachers, when they attended training courses which espoused L1 exclusion theories, the influence of students in the classroom, as well as institutional influences. Once these beliefs were revealed, they were then linked to the classroom actions of the participants via an analysis of their classroom language use. This analysis employed a theoretical framework which had Basil Bernstein’s sociological theories of pedagogic discourse at its core. This framework revealed how teachers’ beliefs influenced the recontextualization of teaching materials into the classroom, changing the nature of the original social and power relations from the appropriated discourse with new, virtual-social and power relations of the classroom. It established that participants with strong beliefs about maximizing English exposure often positioned students so that they had less opportunity to assist in the co-construction of the learning environment compared to participants who valued a larger role for the L1.