Since the end of the Cold War, millions of migrants from Eastern Europe have sought better opportunities in Western European countries, yet few studies have assessed the impact of such moves on these migrants' children. In the aim of isolating a 'treatment effect' of migration on educational outcomes, this study analyzes Programme for International Student Assessment (PISA) scores from 2012, 2015, and 2018 for adolescents born in twelve Eastern European countries and living in eight Western European countries. It employs propensity-score matching within a homeland dissimilation framework, comparing immigrants' outcomes on reading, math, and science assessments to similar stay-at-homes in their countries of origin. In unadjusted comparisons to their counterparts who remained behind, migrant children attain lower scores across all three subjects. Once immigrant children are matched to non-immigrants with similar propensities to migrate, the disparity for math scores disappears, while those for reading and science remain. Disparities are wider for adolescents who come from within the EU, migrate at older ages, or speak a foreign language at home. This paper indicates the need for policymakers and educational administrators to better handle the negative academic effects that migration can have on children from within Europe.