Well for once, I can at least point to this wonderful article by John Taylor Grotto who writes:
Mass schooling of a compulsory nature really got its teeth into the United States between 1905 and 1915, though it was conceived of much earlier and pushed for throughout most of the nineteenth century. The reason given for this enormous upheaval of family life and cultural traditions was, roughly speaking, threefold:
1) To make good people.
2) To make good citizens.
3) To make each person his or her personal best.
Alexander Inglis's 1918 book, Principles of Secondary Education, ... breaks down the purpose - the actual purpose - of modern schooling into six basic functions, any one of which is enough to curl the hair of those innocent enough to believe the three traditional goals listed earlier:
1) The adjustive or adaptive function. Schools are to establish fixed habits of reaction to authority. This, of course, precludes critical judgment completely. It also pretty much destroys the idea that useful or interesting material should be taught, because you can't test for reflexive obedience until you know whether you can make kids learn, and do, foolish and boring things.
2) The integrating function. This might well be called "the conformity function," because its intention is to make children as alike as possible. People who conform are predictable, and this is of great use to those who wish to harness and manipulate a large labor force.
3) The diagnostic and directive function. School is meant to determine each student's proper social role. This is done by logging evidence mathematically and anecdotally on cumulative records. As in "your permanent record." Yes, you do have one.
4) The differentiating function. Once their social role has been "diagnosed," children are to be sorted by role and trained only so far as their destination in the social machine merits - and not one step further. So much for making kids their personal best.
5) The selective function. This refers not to human choice at all but to Darwin's theory of natural selection as applied to what he called "the favored races." In short, the idea is to help things along by consciously attempting to improve the breeding stock. Schools are meant to tag the unfit - with poor grades, remedial placement, and other punishments - clearly enough that their peers will accept them as inferior and effectively bar them from the reproductive sweepstakes. That's what all those little humiliations from first grade onward were intended to do: wash the dirt down the drain.
6) The propaedeutic function. The societal system implied by these rules will require an elite group of caretakers. To that end, a small fraction of the kids will quietly be taught how to manage this continuing project, how to watch over and control a population deliberately dumbed down and declawed in order that government might proceed unchallenged and corporations might never want for obedient labor.
That, unfortunately, is the purpose of mandatory public education in this country. And lest you take Inglis for an isolated crank with a rather too cynical take on the educational enterprise, you should know that he was hardly alone in championing these ideas... Men like George Peabody, who funded the cause of mandatory schooling throughout the South, surely understood that the Prussian system was useful in creating not only a harmless electorate and a servile labor force but also a virtual herd of mindless consumers. In time a great number of industrial titans came to recognize the enormous profits to be had by cultivating and tending just such a herd via public education, among them Andrew Carnegie and John D. Rockefeller.