In this chapter, examples from classroom interaction are presented to illustrate how languagefunctions in and is influenced by the sociocultural setting of the EFL classroom. The chapterfeatures two distinct focal points: First, the predominant use of English by the teacher and theminimal use of English by the students are proposed as instrumental activities where English canbe considered a mediating semiotic tool. I suggest that English-language interaction in the EFLclassroom represents Vygotsky‘s concept of a social semiotic tool that is specifically related to aninstitutional context (Wertsch 1998). Conversely, the second focus of the chapter is on theinverse use of Swedish, which mainly features as the students‘ language of social speech and theteacher‘s language of regulatory, disciplinary discourse. The teacher‘s code choice and theestablished practice of code-switching thus serve to redirect the students‘ focus, either toengaging in the learning of English, or to behaving according to the institutional context.