This article traces the theoretical foundations of student agency across decades of educational research and proposes a multi-dimensional model for understanding it in practice. Vaughn defines agency as encompassing dispositional, motivational and positional dimensions — the capacity and willingness to act purposefully, make decisions and reshape learning contexts. She argues that structural inequality in schools has historically denied agency, particularly to students of colour, students in poverty and English language learners, and that accountability-driven reform has further narrowed the conditions for agentic learning. The article makes the case for redesigning classrooms as spaces where students and teachers co-construct learning, arguing that agency is not a luxury but a precondition for genuine engagement.