The paper presents the results of research conducted among Russian Roma children. Two groups of children, 6-8 years and 8-10 years old, were tested with a Romani Language Assessment Test. The study was conducted in a Roma settlement of a small town not far from Moscow. The children were tested on different grammatical categories in Romani as their home language. The grammatical knowledge of the children about their home language is not considered to be used by the Russian teachers in classroom. The frame of Cummins (2015) “teaching through an intercultural lens” is taken as the starting point of the research. The research results showed that the Roma children at the age between 6-8 years know the most complex grammatical categories of Romani as their mother tongue, however children’s knowledge is not used by the teachers at school environment teaching Russian. There are no lessons in Romani as the mother tongue strengthening the children’s linguistic and cognitive abilities.