Teacher's code-switching and bilingual children's heritage language learning and cognitive switching flexibility.

To code-switch or not to code-switch? This is a dilemma for many bilingual language teachers. In this study, the influence of teachers' CS on bilingual children's language and cognitive development is explored within heritage language (HL) classes in Singapore. Specifically, the relationship between children's language output, vocabulary development, and cognitive flexibility to teachers' classroom CS behavior, is examined within 20 preschool HL classrooms (10 Mandarin, 6 Malay, and 4 Tamil).