The goal of the review of studies in 10-12-year-olds is to solve practical problem of optimal conditions of education for them. The data are controversial. 10-12-year-olds are different from junior schoolchildren but at the same time they need gradual environmental changes for non-trau-matic transition from junior schoolchild's state to adolescence. The author argues that the principal motive power for such a transition in psychic development is reflection. The reflection serves child's self-consciousness, child's ability for self-development. It must be taken into account when the problem of individualisation in learning activity is considered.