Research on code-switching in bilingual classrooms now spans almost two decades. It has been cross-disciplinary in nature and has thus reflected different currents of influence: from educational research on classroom interaction and teacher talk styles and, more recently, from conversational analysis, pragmatics and the ethnography of communication. It has also been international in nature: the early studies were carried out in the United States in bilingual education programmes for linguistic minority children. The 1970s and early 1980s saw the development of a substantial body of classroom-based research in this particular context. However, since the early 1980s, research on bilingual classroom processes has also been undertaken in other bilingual and multilingual settings such as Canada, South America, Europe, Africa and South East Asia.

Most research has been undertaken in settings where there is an ongoing debate about language education policy: in situations where a new form of language education programme has been implemented or where there has been a change in the medium of instruction or, in contrast, in situations where a change in medium needs to be considered because current policies are inappropriate. The principal motivation in undertaking most classroom-based research seems to have been to establish how language education policies are being translated into communicative practice in the day-to-day cycles of classroom life. As Merritt et al. have pointed out: ‘Determinants of language choice and code-switching in the classroom are necessarily more complex than can be “legislated” by language policy on medium of instruction’ (1992: 105).