There has been a remarkable neglect of instructed foreign languages in sociolinguistics, and this can be attributed to a traditionally ‘reflectionist’ view of the relationship between language and social structure, to a preoccupation with the home-school interface, and to the dominance of what Bernstein (1996) calls the ‘social logic of competence’. In combination, these concerns provide little scope for seeing how the value and social indexicality of a school foreign language (FL) might be reshaped within the micropolitics of classroom interaction, or how an FL might serve as a significant resource in the maintenance and accumulation of vernacular prestige. More recent conceptual developments, however, make processes like these more visible, and this is illustrated in an analysis of the impromptu use of German among adolescents in a multilingual school in inner London, where the aesthetics of performance (in R. Bauman's sense) play a significant role, both in the negotiation of identities and in the repositioning of an official code at school.