Vietnam has achieved near-universal access to compulsory schooling over the past two decades. However, inequalities between ethnic majority and minority students are stark at post-compulsory levels, where progression is selective based on academic criteria and ability to pay. In this article, we adopt a mixed-methods approach to examine quality and equity for ethnic minority students in upper secondary education. Across five provinces, we find that ethnic minority students attend "less effective" upper secondary schools than ethnic majority students. However, an in-depth case study of an ethnic minority boarding school in Lao Cai province provides an example of positive deviance. Guided by a targeted affirmative action policy, the provincial government invests a relatively high level of resources to provide fee-free, high-quality schooling for gifted ethnic minority students. We consider the extent to which such policies can redress socioeconomic inequalities in Vietnam, and wider lessons for creating more equitable education systems.