Alexander Inglis's 1918 book, Principles of Secondary Education makes it clear that compulsory schooling in America was intended to be what it had been for Prussia in the 1820s. John Taylor Gatto explains that the work of Inglis's, who was a Harvard professor with a Teachers College Ph.D., positions school as a fifth column into the burgeoning democratic movement that threatened to give the peasants and the proletarians a voice at the bargaining table. Modern, industrialized, compulsory schooling was to make a sort of surgical incision into the prospective unity of these underclasses. Divide children by subject, by age-grading, by constant rankings on tests, and by many other more subtle means, and it was unlikely that the ignorant mass of mankind, separated in childhood, would ever reintegrate into a dangerous whole.
In his essay Against School and book The Underground History of American Education, Gatto explains the six basic functions of school outlined by Inglis.