As a result of globalisation and mass migration, suburbs and schools around the world are becoming increasingly multiethnic, multilingual places. Yet there is still relatively little linguistic research on how language is used in everyday interaction in these multilingual communities. In this paper, I explore the strengths and limitations of traditional language maintenance research for understanding language choice in the school setting and highlight the importance of also considering the ways in which school students learn and draw on community languages other than those spoken by their families. I further argue that understanding the ethnic composition and internal dynamics of the school community can shed new light on how linguistic practices evolve as they do. These points are illustrated through a case study of the language practices of 20 migrant-background students attending at one highly multiethnic Melbourne suburban high school, where around 95% of students speak a language other than English at home.