Based on the data from the Third Regional Comparative and Explanatory Study (Tercer Estudio Regional Comparativo y Explicativo, TERCE), the degree of educational inequality, defined as the strength of the association between the socioeconomic and cultural levels of the students’ families and the performance on math and reading standard tests, is analyzed in this study. The correlations between the results in math and reading tests of students in 6th grade, and the indicators of both the socioeconomic level of the students’ families and the socioeconomic composition of the schools, are analyzed. Multilevel models of three levels (country, school and student) are used. The analysis also allows to estimate the extent to which the school factors may influence the unequal distribution of learning. The study concludes that the socioeconomic composition of student population in school is the main factor explaining the inequalities in performance among schools. After discounting the effect of socioeconomic variables, the proportion of learning inequalities that could be affected by the proper educational variables is drastically reduced in the countries participating in the TERCE as a whole. The image for the countries as a whole is also observed for most of the participating countries.