I did something not quite that bad, but similar. There's an author named Carl Hiassen who writes youth fiction that my son really liked. They are all written about protecting animal habitats and have cute titles like Hoot (about owls), Flush (about fish), Chomp (about alligators), etc. So I was in a used bookstore and saw one of his books called
Puppy, bought it for my son, and sent him to school with it.
Turns out, Carl Haissen writes some adult fiction as well.
Puppy is about an ecoterrorist torturing a lobbyist's dog until he cancels an environmentally unfriendly development project.
Page one is a discussion between two poachers talking about how Chinese people believe Rhino horns are better than Viagra. But in more earthy language.
I got a call from the teacher that day.
Edit: Does this site automatically insert barfing emojis every time I type the word s-i-c-k
?