P. P. Blonsky's opinions concerning solution of global teaching and educational problems - still urgent nowadays - are considered. The author presents also the principles introduced by Blonsky in order to deal with those problems: the principle of development, the principle of comprehensive study of a child, the principle of humanistic attitude to the developing personality, the idea of the working politechnical school, his insistence on synthesis of pedagogical and psychological approaches in educational work. Examples of effective use of psychological data in school are cited.