[maxerickson]

The scales are made up. Many of them are formulaic, counting sentence length or syllables or whatever and digesting that into a number.

https://en.wikipedia.org/wiki/Readability_test links various measures.

I'd be curious to go back and see what and how much my grandfather read in ~1910, after he stopped school in the 8th grade.

[sp332]

When my grandpa got the news that he was going to ship out to the Pacific in WWII, the CO said to the men: "Gentlemen, there is a time and a tide." None of them had more than a sixth-grade education and they all knew what poem he was referencing.

Edit: it appears I have misquoted it myself, or I can't find the reference. It's probably the Shakespeare thing though.