Years ago in high school I observed that there appeared to be no great works of literature that were not in the public domain - because the school book publishers don’t want to pay royalties to anyone, and to a lesser degree nobody wants to do literary analysis of a living author who can dispute their interpretation! Admittedly a little cynical but I think there is a lot of truth to both.
I was also annoyed at all the “yoda speak” translations of ancient literature we had to read whereas any student would be graded down for not putting their parts of speech in the English order.
Then you have things like Candide that would be considered super offensive in the US - where a friend of mine once had a summer job airbrushing away cow udders from a school textbook because the state of Texas (which buys the most text books) felt they were too suggestive. (A few decades ago but Texas still decides what goes in most school text books by virtue of being the largest consumer)
I don't think there's that much truth to your observation.
"The Great Gatsby" only entered the public domain last year, while its Wikipedia entry says it "was part of the assigned curricula in the near majority of U.S. high schools".
"'The Grapes of Wrath' is frequently read in American high school and college literature classes due to its historical context and enduring legacy" says its Wikipedia page, and it's still in copyright.
In 1981, "Catcher in the Rye", according to its Wikipedia entry "was both the most censored book and the second most taught book in public schools in the United States." Salinger didn't die until 2010.
I was also annoyed at all the “yoda speak” translations of ancient literature we had to read whereas any student would be graded down for not putting their parts of speech in the English order.
Then you have things like Candide that would be considered super offensive in the US - where a friend of mine once had a summer job airbrushing away cow udders from a school textbook because the state of Texas (which buys the most text books) felt they were too suggestive. (A few decades ago but Texas still decides what goes in most school text books by virtue of being the largest consumer)