The present article examines the general debate on curriculum differentiation and individualisation. Based on a policy ethnographic case study of class 9a at Forest School, it critically analyses how curriculum differentiation and individualisation are enacted in and interfere with classroom practice. The results show how Forest School's curriculum model on differentiation and individualisation has created and reproduced a system in which different knowledge is available to different groups of pupils. In practice, owing to this policy, some pupils are categorised as successful, some as adequate and some as failing. The analysis also shows that this practice creates differentiation in relation to school achievement and grades, but foremost that pupils in this class of 9th graders are paying a high price for their schooling, in the form of underachievement and social inequality.