Among the more relevant questions in educational research is how the governments and policy-makers in transition countries address the high educational inequality inherited from the past and what policies they develop in order to reduce the strong effects of the background family and the type of school on students' achievements, their aspirations and their chances of succeeding in the most important educational transitions. This paper addresses one of the most topical issues in this area, namely the social selectivity of Czech basic and secondary education. Special attention is paid to the role of 'multi-year' gymnasia. The results of analyses carried out on data from the Programme for International Student Assessment 2000 study corroborate the initial hypothesis according to which multi-year gymnasia, introduced into the Czech educational system after 1989, represent one of the main sources of the variation in students' achievements at the end of compulsory education. However, this variation can be almost entirely accounted for by the specific socio-economic background of the students. The same holds true for their future aspirations. The results of the analysis support the conclusions of the OECD Review of National Policies for Education from 1996.