This study deals with some theoretical problems concerning the raising of the effectiveness of education at the socialist school. In the first part viewpoints criteria are formulated for judging the effectiveness of education. In the first place the results of optimum instruction at the socialist school are characterized. Stress is laid on the unity of basic theoretical and practical pieces of knowledge acquired and the skills of a concrete and more general nature, of mastering the ability to think independently, to search and discover, to learn and work, of shaping and reinforcing the scientific world outlook and moral and character traits of the man of the socialist epoch. These educational results are to be achieved with the utmost time economy, with optimum efforts being exerted by pupil, teacher and society as a whole, and with the optimum number of pupils in a class, who form an optimum heterogeneous group, suitably combined with a homogeneous group. In conclusion of this part emphasis is laid on the principle of being exacting, which is applied with regard to the pupil’s as well as the teacher’s work, and the principle of socialist optimism and humanism, which is to characterise all life in a socialist society. The second part of the study deals with some theoretical and practical problems connected with searching for ways and means of achieving greater effectiveness of education. The starting point is the assumption that if education at the socialist school in the abovementioned conception is to be more effective, it will not do to improve only certain aspects of the educational process, but education as a whole, the whole system of education. The study goes on to characterize some elements (aspects) of the educational process (the subject-matter, the work of the teacher and the work of the pupil, the aim of the instruction, its conditions and means) and to search for fundamental relationships between them. Some aspects of these relationships are characterized by means of principles. The study deals in detail with the principle of the unity of moderness, progressiveness of educational aims and their tradition, the principle of integration and differentiation, the principle of the unity of theory and practice, the open and closed (compact) system, the principle of the unity of social, collective and individual interests and needs, the principle of the unity of the teacher’s leading role and the pupil’s activity and independence. At the same time it is pointed out which of these problems are being verified at the experimental school of the Educational Institute of the Czechoslovak Academy of Sciences.