I explore the ways in which language ideologies are transformed when they are transplanted to diasporic settings as a result of migration. I examine the labelling of Cypriot Greek features as "slang" by young British-born speakers of Greek Cypriot heritage. Drawing on the analysis of data collected in a Greek complementary school in London, I suggest that "slang" is applied to Cypriot Greek through a process of re-enregisterment that redefines the contrast it forms with Standard Greek in the model of the "slang" vs "posh English" binary, which is local to the London context and is constructed along the lines of the ideological schemata of properness and correctness that also define the opposition between Cypriot Greek and Standard Greek in Cyprus. I propose that the policy and practice of teaching Greek in the school is a key enabler in this process as it constructs Standard Greek as a language that can and must be written and Cypriot Greek as a language that can only be spoken but never written. This allows complementary school pupils to draw links with institutional discourses they are exposed to in mainstream education about the inappropriateness of including elements labelled as slang in their writing.