This thesis is a study of language use in English language classrooms in primary schools in Hungary. The focus of the study is on the use of the target language (English) and the mother tongue (Hungarian) by the teachers and the learners. The teachers are all Hungarian native speakers, with varying levels of competence and previous experience in communicative language teaching, and this presents a challenge to the adoption of a communicative approach to the teaching of English. The National Core Curriculum endorses the communicative approach, with the expectation that the target language will be used as much as possible. However, in practice, the mother tongue is widely used in these classrooms, both by the teachers and by the students. There is therefore a conflict between policy and practice: the policy is that the target language should be used wherever possible, whereas the practice is that the use of the target language is limited to predictable and routine contexts. It is this conflict which constitutes the central question which is addressed in this thesis: how do teachers resolve the conflict between what they are expected to do, and what they feel capable of doing. Data from classrooms and interviews were collected and analysed, using both quantitative and qualitative techniques. The focus of the analysis was on the amount and function of the use of the mother tongue by the teachers. Comparisons were drawn between teachers of Grade 4 pupils who started to learn English in Grade 1 and those who started in Grade 4. This analysis is complemented by evidence concerning the teachers‘ beliefs and understandings about the pressures and constraints which affect their teaching of English to young learners. The results suggest that the possibility of communicative language teaching in these classrooms is constrained by various factors, including the limitations in the children‘s cognitive capabilities and the proficiency level of the children, and the teachers‘ preference for using their previous methods which included grammar, translation and memorisation; also by curriculum requirements such as the use of the textbook, and the necessity to prepare the children for examinations. The implications of these findings for curriculum development in foreign language teaching in other comparable contexts are discussed.