Preserving the unique contours of cultural communities is integral to the rich weave of our collective human heritage. However, the postcolonial United States (US) educational paradigm, reflected in curricula and standards based on white middle-class norms, has a flattening effect on the vibrancy of diverse languages and community traditions. Based on their own research, the authors demonstrate that, for distinctive populations like Indigenous groups, research-based educational interventions can actively inhibit learner achievement and suppress cultural vitality. This article presents examples of how "Diné" (Navajo) public schools are affected at system, teacher and individual levels, illustrating how, in a specific cultural milieu, some research-based "best practices" are not in fact for the best. Each example highlights some of the ways in which "understanding context" is an essential ingredient paving the way for student success. The authors argue that in order to optimise the potency of educational innovations developed for Indigenous learners, interventions must adhere to a higher standard of assessment practice. They suggest employing local testing and incorporating stakeholder opinions as part of the strategic design of measuring students' learning progress, as a way of responding to the particular needs and dispositions of a community's unique learners.