Investigated children (6-7 year old) were divided in accordance of their school marks on 3 groups: "excellent" (average mark from 4,6 to 5,0), "good" (average mark from 3,6 to 4,5) and "poor" (average mark from 3,0 to 3,5). Specified groups were compared upon their psycho-physiological and morpho-functional factors. As a result was realized that compared groups were distinguished on the source condition of organism, moreover in the "excellent" group greater amount of children have an average physical development level, with good cardio-respiratoric reserves, strong nervous system, with more high mental work capacity, than in the other groups; mental work capacity grow in all groups by year end, but in greater degree in the "excellent" group; at the school year end the "excellent" children group tired mentally in less degree, than the other groups.