The centenary of the foundation of the International Workingmen’s Association (the First International) has led the author of the article to express some thoughts about the theoretical legacy of this organisation in the field of education. Against the background contemporary events, and especially the discussions on this question in the period of the Geneva Congress of the International in 1866, the author points out the meaning and significance of that part of Marx’s address to the General Council’s delegates which deals with the education of children and working adolescents. It contains the essence of Marx’s fundamental ideas, which, with their theoretical principles, were far ahead of contemporary thought, and which, in many respects, have not lost their significance even for our modern, advanced socialist society. It concerns, above all, Marx’s conception of polytechnical education, which is now one of the basic and, at the same time, one of the most delicate problems of our time. In this connection the author expresses his concern whether inadequate, and often very superficial knowledge of Marxist-Leninist theory possessed by a certain part of our educationalists, does not throw the doors wide open to the unwanted penetration of that unilaterally ≫craftsman like≪ approach to polytechnical education, which Marx himself repudiated so resolutely in his struggle against the Proudhonists. It would certainly be very useful if all those who are in any way concerned with education in practice, mainly our teachers, went more deeply into this question, which the author himself, as an individual, is unable to tackle.