Student self-assessment has been framed as a way to address the issues of power in assessment in higher education. However, rarely has self-assessment been used to challenge the broader political issues of grading. In this study, I introduce the concept of summative self-assessment, drawing on self-grading as a practice that seeks to disrupt the usual power relations of assessment. The summative self-assessment model was implemented in the context of undergraduate mathematics, after which 26 students were interviewed. Using three theoretical frameworks of power, an elaborative coding process was conducted to examine how students' conceptions of summative self-assessment reflected either empowerment or disempowerment. The results underline the complexity of disrupting the power relationships in assessment from inside the system, calling for systemic changes in grading mechanisms.