The article presents the results of a study of age peculiarities of the development of coordination abilities of pupils in grades 2-4. According to the purpose of the study, we studied the age peculiarities of the development of the equilibrium function and determined the structure of the relationship of coordination abilities and biomechanical factors. Altogether 80 primary school children were involved in the educational experiment. Methods of research applied were as follows: analysis and systematization of medical and sports publications; study and generalization of advanced pedagogical practice on the issue of the investigation of the coordination abilities of primary school children; testing, educational experiment, methods of mathematical statistics. Analysis of the results made it possible to identify the level of static and dynamic equilibrium in the process of physical education. The equilibrium function in primary school pupils develops quite intensively from grade 2 to grade 4. We found that with age in children, there is a functional improvement of the reflex mechanisms that are responsible for maintaining balance. In our study, we found that body length and body weight do not have a significant influence on the ability to keep static and dynamic equilibrium. The results of our studies testify to a significant impact of visual and vestibular analysers on the ability to keep body position. Exercises that were performed with eyes closed had a large amplitude of body vibrations and impaired stability in all age groups. It is noteworthy that the influence of the visual analyser somewhat decreases with age. The analysis of coordination abilities shows a statistically significant difference (p 0.05) between boys and girls during the tests. Although the indicators of static equilibrium in girls of all ages had insignificant predominant features, and, on the other hand, in boys, the results of dynamic equilibrium were higher.