Adopting a sociocultural theoretical framework and based on ethnographic data from two primary schools, this article seeks to answer the question: what meanings about inclusion and exclusion are encoded in school and classroom practices? It documents the (inclusionary and) exclusionary pedagogic processes that influence learning and children's participation in the learning opportunities on offer to them. From their analysis of observational, interview and documentary data, externally-imposed and monitored regimes of assessment are what really matters in the school lives of the year six children in the authors' fieldwork schools. Assessment, narrowed to testing, defines the school day, the curriculum, the teacher's responsibilities, the pupil's worth, the ideal parent, and what counts as ability; it pushes towards a particular type of learning at the expense of other types. The article begins with a brief theoretical and methodological account of the study and a note on each participating school. It then suggests and discusses models of 'SATurated pupildom' that are supported by the data. Versions of learning and ability as well as teacher subject positions that variously fit with the demands of summative assessments for accountability purposes, but that do not square with valuing diversity, are also discussed. The conclusion briefly considers the findings in the context of a macro-culture that circumscribes what schools and teachers must value most and in relation to tensions within New Labour's push for standardisation on the one hand and inclusion and social justice on the other.