Before one develops anything, one should have a pretty clear idea of its purpose. What is the thing you are building supposed to do? It makes no sense to talk about the structure of something without having in mind, first, a clear idea of its function, or purpose. Form should follow function.
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.