Student agency in assessment is evident when students make assessment choices, and their voices inform decisions. This paper presents an in-depth case study of a high performing school that sought student voice to reform its assessment culture to enhance student agency. Secondary students in an Australian school were invited to draw a visual metaphor: if assessment were a food, what would it be? Responses were analysed to identify: What can be learnt about assessment culture from students' drawings and comments? And how did student voice inform changes in school assessment practices and assessment culture? Six years later, the student ideas were revisited by a school leader to identify how cultural and structural conditions for student agency within the assessment culture had changed. Using visual methodologies with students provided insightful commentary on how assessment practices may be modified to support learning and the challenges of engaging in assessment culture reform.