I have not actually seen any first-graders reading Sartre or Nabokov. Perhaps they're not that interested?
What about gay or subversive authors? Will kids not be able to read The Importance of Being Ernest? How about the poetry of John Donne? Lord Byron?
What about that children's classic:
Vladimir and Estragon Have Two Mommies But Will Still Die Alone, Like Everyone Else...Even You!