This paper revisits the notion of 'legitimate language' [e.g. Bourdieu 1977. "The Economics of Linguistic Exchange." "Social Science Information" 16 (6): 645-668] as it relates to multilingualism in educational contexts. Since Heller [1996. "Legitimate Language in a Multilingual School." "Linguistics and Education" 8: 139-157] developed the notion of 'legitimate language' to encompass issues of language choice, there has been a consensus that a legitimate language is a language that is "appropriate" in a given situation. However, a crucial issue remains to be addressed, namely that of knowing what benchmark do classroom participants use to know when a language is appropriate, that is, legitimate or not. To address this issue, this paper takes as an example the case of an induction classroom for newly-arrived immigrant children in France where multiple languages have been observed. A Conversation Analysis of a set of audio-recorded interactions reveals that whilst languages other than French are not legitimised by top-down language policies and ideologies held at the societal and institutional levels, they are nevertheless seen as legitimate according to the local 'practiced language policy' [Bonacina-Pugh 2012. "Researching 'Practiced Language Policies': Insights from Conversation Analysis." "Language Policy" 11 (3): 213-234]. This paper thus argues for a multi-layered understanding of legitimacy and shows how in the classroom under study, and possibly in other multilingual classrooms, practiced language policies play a key role in the legitimisation of multilingual language practices.