This paper reports on a three-year action research project action investigating the relationship between assessment as a social structure and the agency of students within a preparatory course for postgraduate international students at a UK Russell Group University. Action research into academic writing assessment within this highly constrained context was informed by critical realism, which allows for impacts of assessment on students to be conceptualised as 'absence', in this case of agency and for change to be understood as the 'absenting of absences.' An initial reconnaissance stage precipitated the implementation of an intervention called processfolio. The first intervention cycle involved one class of 14 students; the second cycle widened the scope to three classes. A range of data sets was employed at each cycle, including interviews, and the students' processfolios. Students demonstrated varying stages of critical consciousness of assessment as a constraining social structure and, through the processfolio, some found space to resist and make agentic choices. Through the iterative process of action research, it became clear that the real purpose of the processfolio was to use assessment itself as a tool to absent the negative impacts of these assessment practices, thereby subverting and disrupting assessment as a social structure.