«Children’s writing» in Russia and in the Soviet Union are without a doubt sources as new as they are precious, beyond any disquisitions on the nature of the sources, on adult influence on the child and on the spontaneity of the child in the learning process. For this reason the present essay analyses the different typologies of «children’s writing», produced at school, in the sections of the Pioneer Organisation, in the orphanages and in the family itself, starting from the general context of mass alphabetisation. For the first time in the history of the Soviet Union, this reveals that children were able to not only read but also to write, and could use writing to learn complex knowledge, to communicate with adults, and to recount dramatic experiences of the Second World War. This essay aims to grasp the way in which these sources can shed new light on our knowledge of the history of childhood and Soviet education in general. It is divided into three parts: the first analyses school exercise books (dealing with the history of literature), valuable for the analysis of the evolution of teaching methodology and the content of Soviet school reform. The second part deals with letters sent by adolescents to the governmental Authorities, which are useful for reconstructing the process of development of the first Pioneer Organisations for communist adolescents in the interwar period. The third studies diaries and war stories which bear witness to the injustices of Stalinism and the dramatic experiences of the Nazi occupation. The enormous quantity of «children’s writing» preserved in the Archives are evidence of the almost sacred value attributed to writing as palpable evidence of the great heroic deeds of the Soviet people in the edification of communism and in their defeat of Nazism.