With a primary consideration for the case of Sweden this presentation will address the increased diversification of classrooms in recent years and how this has placed additional demands upon teachers who strive to facilitate the learning and participation of all pupils. It is based on research into processes of identifying, categorising and responding to the perceived individual differences of learners. Relatively sophisticated means of responding to individuals are described, but so too are processes of categorisation that are shaped by institutional and policy demands that have little to do with enabling individuals to flourish. The presentation concludes by considering whether mass education systems such as those in England, Sweden and the other Nordic countries can ever hope to respond effectively to individual differences.