The people who started the first widespread systems of compulsory schooling—the systems that still provide the model for our schools today—had a very clear idea of the purpose. These people were Protestant clergymen, in Europe and the American colonies, at the time of the Protestant Reformation, in the late 17th and early 18th century. They stated clearly that the purpose of schooling was indoctrination and obedience training.
Their firm belief was that children are naturally sinful and the only way to salvation was through Biblical indoctrination and the suppression of free will . The schools they created were well designed for that purpose.