A figure that often jars a lot of people is that, according to the 1940 census, only 25 percent of the adult population of the US had finished high school. It was much more common for 1920s and 1930s kids to graduate than it had been for their parents, but the general American adult population of the time had seen no education beyond the sixth, seventh, or at most eighth grade. And the quality of that education varied according to where you lived -- a kid growing up in a city in the 1910s and 20s had a decent chance of getting a good elementary education,albeit one based more on the rote memorization of facts than on understanding of the theory underlying those facts, but a child growing up in the rurals would likely be taught to read and write, after a fashion, and perhaps recite a bit, but they would have little awareness of much else beyond their own circumstances. Rural folk often had a deep and abiding prejudice against "book larnin'", which continues to manifest itself right down to our own time -- witness the deep strain of anti-intellectualism that dominated the 19th Century populist movement and continues to dominate the current populist movement.
I think the old Judge offers an interesting blend of attitudes. On the one hand, he did make a lawyer out of himself instead of living out his life as just another rawboned Missouri dirt farmer, but on the other, you can hear the venom spitting out of his mouth whenever he talks about those "haaaaagher critics and their eddddjahcations." I think that's a perfect reflection of the two-minded attitude working-class Americans of the early 20th Century had about education.
I was trying to remember the name of the guy who wrote that "Proletarian" piece -- I read that years ago and thought he was pretty much on the ball. That was still early on in the Knorr era, but the two-fisted rolled-sleeve Witness was already an endangered species by the mid-fifties, giving way to the Organization Man in the Grey Flannel Suit. Nothing could better mirror the change in America itself -- from an overwhelmingly working-class, left-leaning country before the war to an increasingly status-conscious middle-class right-leaning country during the postwar era.
As far as the Cohn piece on race goes, I don't know the exact percentage, but there was a very heavy proportion of black witnesses at the time when Stroup was writing, at least in the New York City-area congregations he investigated, but he pointed out, as Cohn did, that "Negroes" were generally not given leadership roles in mixed congregations. It's interesting to read the 1930s yearbooks and see how the Society dances around the race question, with a lot of mealy-mouthed talk about how "of course in Jehovah's eye there are no race differences, but due to the prejudices of man it was thought best to specially organize the work amongst our colored brethren." Segregated assemblies were being advertised, even into the North, well into the 1940s.