How strategic use of L1 in an L2-medium mathematics classroom facilitates L2 interaction and comprehension

There has been an increasing interest in and hence a growing number of research studies on content and language integrated learning (CLIL) over the past two decades. One of the on-going debates in CLIL is on bilingualism versus monolingualism, or the role of the first language (L1) in subject teaching. So far, very few research projects have been carried out in Asian L2-medium classrooms where there are significant differences in the learners' L1 and L2. Adopting an exemplary case study approach, this study investigates a bilingual teacher's strategy use in a mathematics L2-medium classroom in Hong Kong. Through analysing classroom observation data, teacher and student semi-structured interviews and artefacts, it was noted that the teacher made strategic use of L1 to mediate her students' gradual adaptation to the shift in medium of instruction. Methods that the teacher used included ones that resemble what L2 teachers would employ in language teaching: noticing, syllabification, morphological cues, think-pair-share, vocabulary-building strategies, questioning techniques, immediate correction and others. Results of the current investigation support as well as extend the findings of previous studies and have important reference value for bilingual teachers, teacher educators, policy-makers and CLIL researchers.