Can you back that up with something? Every educational standard I have seen from 1940 vastly exceeds today, it’s not even close.
Most of our WWII soldiers were NOT illiterate or even close.
I have a 7th grade Texas History textbook from that era, and it would be a tough book for most adults to use today. I have a math book from that era also, same story. I have a school text of farming methods from the 1920s, same story.
I don’t think you can back up that claim.
My father went to public school in Brooklyn and he had to learn Latin.