This article empirically studies the impact of bilingualism on educational achievements. This relationship has been thoroughly studied in a number of countries around the world, but not in Russia. We used a sample of 709 ethnic Tatar school students aged 15-16 (in the ninth grade) in the spring of the year 2010. We found a positive significant effect on school grades based on logistic regressions, and controlling for family background characteristics, school characteristics, psychological attributes, health issues, peers, gender, and the impact of the capital city Kazan. Oral bilingual children, who use Tatar language at home, are more likely to obtain the highest grades in literature and chemistry classes, and they have lower probabilities of obtaining the lowest grades in Russian language, literature, geometry, and physics. We did not find negative impacts on school grades due to the use of Tatar at home. Therefore, we found evidence in favour of bilingualism and against the assumption of Russian policymakers that bilingualism threatens the knowledge of Russian.