This study examines how preservice teachers (PTs) engage in a mathematics simulation focused on iconic interpretation. The data reported herein show how a clinical simulation illuminates PTs’ mathematical knowledge, instructional abilities, and practices in need of refinement. Simulations allow the authors to see PTs practicing, making mistakes, and using data to build from within and from each other. For educators vested in the development of future educators, the simulation concept and resulting data sets are extending our views of ‘clinical preparation’.