This paper examines the sociolinguistic situation of a multilingual secondary school in the Barcelona metropolitan area and examines the language practices of both students and educators. Following a critical sociolinguistic ethnography perspective, it understands practices as constructing the socio-institutional order of the school, and language as constitutive of social processes. The analysis of the data shows that the students, the majority of which are of migrant background, systematically fail to employ Catalan, the language of schooling, and that the teachers refuse to enforce official linguistic norms. Rather than considering it exclusively a language issue, we claim that language is an index of a process of constructing the school as 'different' and the school body as non-academic. In the analysis of discourses and practices, social class emerges as one of the grounding motivations for such 'difference', which leads to low academic demands, a life skills educational perspective, and lack of competence in Catalan, with serious consequences for students’ social access. (PsycINFO Database Record (c) 2016 APA, all rights reserved)