Socialist Sunday Schools (SSS) were set up to replace or augment Christian Sunday Schools in the United Kingdom, and later the United States. They arose in response to the perceived inadequacy of orthodox Sunday schools as a training ground for the children of socialists and the need for an organised, systematic presentation of the socialist point of view to teach the ideals and principles of socialism to children and young people.
In the US, a Sunday School movement linked to the German-American socialist movement emerged in New York and Chicago in the 1880s and again on a broader scale as part of the Modern School Movement during the first decade of the 20th century. An even larger network of American Socialist Sunday Schools, closely paralleling the British movement, was launched by members of the Socialist Party of America during the first two decades of the 20th century.