Trish O’TooleIn this short communication, I provide an example of a student’s work to illustrate the power of assessment for learning. This approach has been adopted to support both teachers and students to come to aspects of mathematical learning. Drawing on the literature on assessment and how it is integral to learning rather than as the end product to show what learning has occurred, I provide examples of one case to illustrate the power of assessment for learning. By drawing on aspects of second generation activity, I provide examples of aspects of the learning milieu to frame the analysis of the student’s work. Through the use of activity theory, a coherent approach to understanding the complex milieu of classroom learning environment can be developed.