This paper reports on an ethnographic study of classroom practices in a township school in the Wesbank settlement near Cape Town, South Africa. Focusing on the ways in which a multilingual and highly diverse student population confronts English literacy, we argue for a view in which norms are seen as emergent and contingent on occasion, place, social and sociolinguistic environment. The school, Wesbank High, is by all standards a "peripheral" school in a marginalised community struggling with very serious socio-economic marginalisation corroborated with a dearth of high-quality public provisions in the settlement. The school is one of these provisions, and teachers and learners share ideals of upward social mobility, often crystallised in discourses on English as an instrument of spatial and social mobility. Learners' writing in English, however, displays many features of "grassroots literacy"--sub-elite literacy characterised by orthographic, syntactic, lexical and pragmatic peculiarities. These peculiarities--"errors" when seen from a punitive and homogeneist viewpoint--appear to be shared by learners and teachers alike, both groups being inserted in a particular, peripheral economy of English. "Errors," thus, are "systemic," "normal" and hence "normative," they do not preclude effective and differentiating assessments of learners' performance but are a productive, positive mechanism that allows teachers to reach a degree of effectiveness with their marginalized and heterogeneous groups of learners. We witness the production of locality through peripheral normativity, as well as the creation of a problem of "mobility" when such locally valid forms are deployed elsewhere. These findings have implications for globalisation theory and views of systemic power in Third-World classroom environments.