In this chapter, our context is a co-located Swedish and Finnish medium high school campus. From a posthumanist viewpoint, we study the roles and functions of language(s) in the semiotic assemblages of learning environments and ask how language(s) feature as an integral and material part of the change in the spatial repertoire of learning environments. We investigate how the principle of separation of schools by medium of instruction, typical for Finnish education, becomes undermined through a new multilingual soundscape in the co-located schools, where the school community hears and uses many languages every day. In doing this, the co-located schools not only challenge Finnish language ideologies and practices, but may also promote language learning in a more effective manner than structured, curriculum based ‘planned’ forms of multilingual education. In the long run, the placing of Finnish and Swedish language schools in one location has led to teachers’ recognition of the new assemblage as a resource for pedagogical change.