Indonesian government policy supports the international of education at thesecondary level, consequently more institutions have commenced bilingual programs.Content is taught both in Bahasa Indonesia and English, making code-switching inclassroom discourse. The study was conducted at a single International school inSemarang, East Java, Indonesia. This case study explored in what ways and underwhat circumstances Indonesian teachers and learners use code-switching in theselected bilingual classroom and semi structured interviews with six-bilingual classstudents and teachers at an International secondary school in Semarang, East Java inIndonesia are used to get the data. The finding shows Teachers’ and students’ codeswitchingdemonstrated collectivist phatic functions – for example, teachers codeswitchedto build rapport, remind students and reduce students’ anxiety, and studentscode-switched to show their solidarity and concern for their peers. Thus,interconnectedness was a key characteristic of code-switching by both teachers andstudents. This study argues that code-switching is not just about language deficiency,but involves intentional communicative purposes which support teaching andlearning. It can be concluded that code-switching can be a useful tool to bring aboutunderstanding of unfamiliar concepts and processes as well as the languageassociated with them.