[Aedes]

Accents are regional, and teachers are nearly always from the region where they teach. Furthermore, accents are not 'taught' -- you can still speak perfectly grammatically correct English with a Bronx accent or a Texas accent.

As for this decline after the 1950s, consider that our highways, dams, power grid, internet, etc were mostly built after that point.

Schools DID start at the community level, but government stepped in to standardize curriculum and to guarantee access to all children.