Whatever random book any random teacher bought or was given.
The whole point is that they have to remove ALL books that aren't approved through The Process. Of course there's not going to be a list of those. There isn't some master list of books that are lying around classrooms everywhere.
The rules are whitelisting not blacklisting oriented, so it’s easier to give the set of list that would be allowed, and every other book in existence outside that allowed set is potentially blocked.
The rules would block a book like East of Eden. Pornographic elements and too advanced for kids (even if it isn’t)
The whole point is that they have to remove ALL books that aren't approved through The Process. Of course there's not going to be a list of those. There isn't some master list of books that are lying around classrooms everywhere.