In the 1990s, Greece received, among other immigrants from different regions of the world, repatriates from the former USSR as well as refugees from the same region. This article outlines part of a research study focusing on the children of both Greek and other origins, who emigrated to Greece from the former USSR and who attended primary schools in Thessaloniki between the academic years 1989-90 to 1999-2000. The aim of this article is to compare the performance in language and mathematics of immigrant and repatriate children, who started school in Greece, with children of the same group, who joined school at a later grade, and also to compare the first group of children with their native peers.