This article argues that student voice only achieves its full potential when it is directly connected to student agency — that is, students’ ability to actually influence educational practices, not merely express opinions. Drawing on empirical studies from multiple countries, Cook-Sather surveys three main arenas where student voice can drive real agency: collaborative analysis of classroom practice (e.g., students working alongside teachers to examine and revise pedagogy), participatory research (including youth-led action research where students act as co-investigators), and authorship (students co-writing and publishing analyses of their educational experiences). The paper includes case studies such as Vermont’s “Youth and Adults Transforming Schools Together” (YATST) program and Māori student voice work in Aotearoa New Zealand. It concludes with practical recommendations for teachers, school leaders, teacher educators, and researchers on how to embed genuine student voice into school culture and structures.