Student voice has the potential to prompt creative and transformative teacher professional learning and practice. However, contemporary conditions of education -- including policy priorities and institutional constraints -- shape how student voice is taken up. This article draws on data from an evaluation study of a student voice programme ('Teach the Teacher') as enacted in two Australian schools. Notwithstanding the possibilities of student voice, reductive interpretations of teacher's work risk translating student voice into thin practices; the teacher becomes envisioned as technician who needs to fill their 'toolbox' and find 'what works' by listening to students. Analysing what is said and unsaid about student voice for teacher professional learning in interviews with school leaders and teachers, as well as focus groups with students, this article explores the problematics of mobilising student voice for teacher professional learning. Questions are raised for those seeking to promote reciprocal intergenerational learning in democratic schools.