How much L1 is too much? Teachers' language use in response to students' abilities and classroom interaction in Content and Language Integrated Learning

In Content and Language Integrated Learning (CLIL) classrooms where students' L2 proficiency has not reached the threshold level, teachers have been observed to use L1 to assist students in grasping specific technical terms and abstract concepts. It is argued to be a 'realistic' approach to the learning problems caused by students' limited L2 proficiency, particularly in English-as-a-foreign-language contexts. Nonetheless, researchers have also warranted 'judicious' and 'principled' use of L1 so that both content and language learning are facilitated. The question thus remains is whether teachers can use L1 appropriately to suit their students' needs. This study seeks to address this question. It includes data from 30 Grade 10 lessons in Hong Kong CLIL classrooms, where students' L2 proficiency varied considerably. Using both quantitative and qualitative analyses, this study shows that when teaching students with limited L2 proficiency, teachers used a significant proportion of L1 in lessons to explain the subject content, interact with students and develop students' L2 metalinguistic awareness. In contrast, with students highly proficient in L2, teachers used little L1, mainly to provide translation equivalents for L2 subject-specific vocabulary items. This study thus shows that teachers seemed to be sensitive when making use of students' existing linguistic repertoires.