Here’s a random passage from Christopher Clark’s Iron Kingdom: The Rise and Downfall of Prussia, 1600-1947 that sheds light on some contemporary K-12 policy debates:
But the Halle model remained influential; in the 1740s and 1750s, the educationalist Johann Hecker, a former teacher at the Pädagogium who had been trained at Francke’s Teachers’ College in Halle, founded a network of ‘pauper schools’ in Berlin catering to the neglected and potentially delinquent offspring of the town’s numerous soldiers. In order to ensure an adequate supply of properly trained and motivated teachers, Hecker established a teachers’ college on the Franckean model; he was one of several graduates of the Halle college to set up such institutes in Prussian cities. He also founded a Realschule in Berlin, the first to offer children of the middle and lower-middle classes tuition in a range of vocational subjects, as an alternative to the Latin-based, humanistic curriculum of the traditional secondary school. It was Hecker who popularized the practice of teaching pupils of like ability collectively, so as to maximize the efficiency of the teaching process; this was a crucial and lasting innovation.
Johann Hecker, in other words, pioneered an organizational innovation that allowed teachers to manage larger class sizes. Sort of the Salman Khan of his day. If you’re able to pull this kind of thing off, it then becomes much politically easier to increase the real wages of teachers and therefore hopefully to recruit and retain the best possible people.