We examine how different spatial compositions affect the educational achievement in mathematics of 16-year-old students in Chile, a Latin American country with high inequality and one of the most segregated education systems in the world. Conceptually, we complement the literature on ‘neighbourhood effects’, which typically addresses the influence of concentrated disadvantage, by focusing on concentrated advantage and its influence on educational outcomes. We construct a panel with all school students who took a national standardized mathematics test in 2010, 2014 and 2016 in the Metropolitan Region of Santiago, Chile. We complement it with survey data for the 52 districts of the Metropolitan Region, clustering the districts based on factors such as unemployment, economic inequality, access to services, experiences of violence and stigmatization. Our different identification strategies consistently show that concentrated poverty and affluence are both relevant for explaining educational achievement in mathematics above and beyond individual and school characteristics.