This document is an English-language abstract (approximately 1,500 words) of a book which purposes to elucidate the connection between the development of pupils and their assimilation of knowledge and habits in the experimental grades of a new system of elementary education. Various methods of investigation were used: observation during lessons, analysis of written tests, individual talks with pupils, and experimental psychological methods. The success achieved in the general development of the elementary students using the new system included a high quality of knowledge and habit assimilation in various subjects. However, many individual differences between children were noted within the new framework. The slow learners made as much progress proportionately as the most capable students. Reading, spelling, and music were the subjects used in the experiments. (Author/GDB)