By taking both pupils' and teachers' actions as the point of departure, this study aimed to understand governance within a primary school classroom. Video footage was recorded in an English primary school in which mathematics happened to be the focus. This data was analysed to identify the directions of both governance and self-governance and to help understand the consequences for pupil and teacher subjectivities. Our findings revealed the central role of national testing and inspection policy in constituting staff as 'evidence hunters' and pupils as 'confessant and unafraid producers of evidence'. Both staff and pupils were complicit in creating sufficient space for everyone to fulfil their obligation to be accountable to the school's senior leadership team (SLT), school inspectors and national attainment tests. As a consequence, mathematical knowing was simplified into a discipline of reproducing testable calculation, in which other possibilities of mathematical knowing were foreclosed.