Many students do not recognise in themselves positive learner identities in mathematics and thus exclude themselves from further mathematics education, limiting their life opportunities. In this study, I use a performance metaphor for identity, drawing on G.H. Mead, Erving Goffman and Judith Butler to analyse interviews with students, taken at four time points as they make the transition from primary to secondary school. The question I focus on is "How do you recognise someone who is 'good at mathematics'?" The students' responses reveal that there is a wide variety of scripts available when enacting the role of "good at mathematics", and these include getting high marks, knowing the answer quickly, helping others and demonstrating the confidence to put up their hand to answer questions. Despite the variety of ways in which to demonstrate "good at mathematics", most of the students did not recognise themselves in their own descriptions. This goes some way towards explaining why students may opt out of further study in mathematics, despite high achievement in this subject.