Most of the literature on the development of educational inequality has operated under the achievement gaps paradigm, often assuming that the underlying normative and methodological foundations related to equality and justice in education are a settled matter. In this article, we argue that important normative dimensions are overlooked with traditional mean-based measures, and that metrics that capture students' academic mobility as they progress through school can provide the informational base needed to describe and evaluate these policy and socially relevant aspects. We discuss some key normative principles and methodological dimensions related to academic mobility and provide an empirical example of the mobility metrics presented using a nationally representative data set.