The purpose of the research is to determine features of motor preparedness' classification of 11-13 years old boys considering level of physical exercises' mastering. Material and methods: in the research 11 years old boys (n=58), 12 years old boys (n=76) and 13 years old boys (n=93) participated. The following methods of a research have been applied to solve the tasks: analysis of scientific and methodical literature, pedagogical testing and methods of mathematical statistics. Testing program includes well known tests. Results: Standardized coefficients of canonic discriminant function permit to determine correlation of variables' contribution to function's result. The first function explains variation of results by 80,1% (p<0,001), the second -by 19,9% (p<0,001). It witnesses that it is possible to classify age distinctions of 11-13 years old boys on the base of testing of their motor preparedness considering level of physical exercises' mastering. Discriminant analysis permitted to answer the question: how confidently it is possible to separate one class from the other by the set of offered variables; which of these variables influence the most substantially on specifying of forms; to which form the object belongs on the base of discriminant variables; in what correlation are the development process of motor ability and physical exercises' mastering of children and teenagers. Conclusions: Structural coefficients of canonic discriminant function witness that the essential difference is observed between boys of 11 and 12-13 years old in the level of physical development, speed-, dynamic and static strength, physical exercises' mastering. Structural coefficients of the second canonic discriminant function indicate that the essential difference between boys of 12 and 13 years is observed in the development of flexibility level and vault's mastering. Analysis of coefficients of canonic discriminant function witness that the obtained data characterize the communications of development and the system of children and teenagers' physical training has an hierarchical structure in which the development of motor abilities is subordinated to the process of motor skills' formation.