Physical activity is one of the most important means of forming strong health of a child in the conditions of modern school. Currently, after-school sports activities are an integral part of life of the majority of school children. The objective of this study is to assess the state of posture of Moscow primary school children who attend and do not attend various sports clubs after school. The results of the study have shown that the most favorable sports for forming correct posture in children are figure skating, artistic gymnastics, and acrobatics. In these groups, the number of children with incorrect posture is the lowest, at 6.6% and 25%, respectively. Children involved in sambo and judo have disorders in 39.9% of cases. A high total percentage of posture disorders has been identified in groups of children engaged in martial arts, such as karate, aikido, and boxing (64.5%), sport dance (78.8%), and game sports and swimming (83.1% and 83.2%, respectively). The data obtained in the study allow us to talk about useful and harmful physical activities for the posture of primary school children. However, the largest number of children with posture disorders (96.6%) has been recorded in the group of children who do not participate in sports clubs and whose physical activity is limited only to school physical education lessons.