Together with the quality of the educational outcomes equity of the learning opportunities can be considered a golden rule for every educational system. This paper focuses on the equity in the distribution of learning opportunities in the educational system of Slovenia. Several international databases such as PISA, TIMSS and PIRLS as well as the database of the national assessment are explored to find information about the equity of the country's schools' performance as an indicator of consistent achievement standards across schools. In every country a range of student achievement could be expected. However, the differences in student achievement can pertain to the differences between schools or to the differences within schools, that is, between individual students. An educational system with large differences between schools could be described as incapable of securing consistent standards across schools and of providing equal learning opportunities for all students. However, the differences between countries' educational systems and the methodological differences between the surveys from which the indicators are derived can diminish policy relevance of the comparisons of certain indicators. In this paper we try to explore to what extent is the indicator of equity in the Slovenian educational system stable across different international and national surveys as well as across the cycles of these surveys. Only stable indicators can be seen as higly policy relevant. Operationalization of the equity indicator will be based on PISA approach – decomposition of variance into between school and within school variance using the HLM methodology. The anticipated problem is that among the several international studies do not offer comparable data to operationalize SES indicator. The SES indicator will be operationalized to the best level possible.