Abstract. The period of junior school age (7-12 years old) is one of the important stages of mental development of children. In this article, the main features of the mental development of children of junior school age, as well as the processes of cognitive, emotional, social and personal development are widely covered. The article also analyzes the influence of educational processes, family and environment on children's mental development. A proper understanding of mental development and its importance during early school age will help children become successful individuals in the future