Based on previous studies which have proved the influence of school characteristics on pupils´ performance, this study examines the current policy determining classroom composition established by schools for those pupils who are older than their peer group. The study explores test results and contextualized questionnaires used by the Basic Education Evaluation Program an organ of the State Public Education Evaluation System of Minas Gerais, carried out in 2003, and which demonstrates, by means of analysis of statistical hierarchical linear models, the relationship between classroom homogeneity/heterogeneity in relation to advanced age for a specific school year and pupils´ performance.