The content of a school subject is known to depend on numerous factors — on the demands that life makes on the pupils' knowledge, on the level of development of the particular science, on the psychological and physical possibilities of children of the various age groups, etc. Proper consideration of these factors is an important condition for the most effective training of schoolchildren, for extending their cognitive capacities. But it sometimes happens that this condition is not adhered to for one reason or another. In this case the teaching does not produce the desired results, both as regards the children's mastering the necessary fund of knowledge, and as regards the development of their intellect.