The number of electronic educational resources is multiplying day by day. Though such resources can be used in teaching children, teachers are not aware of their effectiveness thus far. So as to include websites in educational process purposefully and methodologically profoundly, it is important for the teacher to have cognizance of educational tasks that can be solved with the help of electronic resources, methodological functions they perform, and types of training activities they support and initiate. The paper is aimed to reveal the effectiveness of the interactive educational platform UCHI.ru while teaching math to primary school students. The leading methods applied in the research are as follows: testing, observation and analysis of educational process aimed to teach Mathematics to children aged between eight and nine through the use of UCHI.ru interactive educational platform to specify the dynamics of mathematical skills development in primary school students. The paper proves the validity of primary school students’ mathematical training using UCHI.ru interactive educational platform; reveals features in teaching Mathematics to children aged 8-9 with the use of an educational website; identifies possible problem areas in teaching Mathematics using UCHI.ru interactive educational platform. UCHI.ru interactive educational platform, proposed in the paper, improves learners’ motivation, facilitates their search competence formation and identifies gaps in basic knowledge of “Mathematics” as a subject for each student in class. UCHI.ru interactive educational platform can be employed by primary school teachers as supplementary didactic material.