The study deals with the critical assessment of the theory of the British educationalist and sociologist B. Bernstein and other authors concerning the difference between the learning of a language and the educational results in children from different social environments. The article analyses: (1) The contents of the original Bernstein theory, (2) Research based on the Bernstein theory, (3) Criticism of the theory on the language deficit of working-class children, (4) The validity of the Bernstein theory in the conditions of the socialist society. On the basis of several educational and sociological research studies (especially Z. Ferge, 1972, D. Valíková, 1971, J. Průcha, 1974), made in socialist countries the following conclusions were reached: (1) In the conditions of a developed socialist society, where social, cultural and other differences between the respective strata of the population are gradually reduced, the Bernstein theory is unrealistic. (2) The invalidity of the Bernstein theory in the socialist society does not mean that the whole problem of differences in the results of school education given by the different social and ecological (mainly town and rural) environments completely disappears. However the theoretical basis for the research and resolution of this problem cannot be the Bernstein theory of language deficit of the working-class children. The reasons for the educational shortcomings of certain children arise from other than purely language factors. (3) From the methodological aspect the Bernstein theory is of importance for socialist pedagogics by the fact that it points to the need to study the language and communication phenomena in pupils in connection with practical questions of education (e.g. the influence of various educational environments on the communication activity of children, the communication between the teacher and pupils etc. — see J. Průcha, 1971). A logical requirement is a complex, inter-branch approach, linking the educational findings and methods with the socio-linguistic and other ones.