The paper studies whether Russian remains dominant in the education systems of five former Soviet countries. Using regression analysis and data from the 2015 Programme for International Student Assessment, math, reading, and science achievement gaps are estimated and several mechanisms of language-based inequality are examined. The findings imply educational equality across languages of instruction in Georgia, Lithuania, and Latvia. However, language-based educational inequality favoring the Estonian language exists in Estonia, driven by differences in socioeconomic status. Further, in Moldova, Russian languages students outperform Moldovan language students despite being of lower socioeconomic status and despite shortages of teacher supply and school resources.