Key point: the books are still accessible for everyone outside the school!
If we engaged in a lengthy conversation, we would identify inappropriate content that you believe should have restricted access to children.
We would likely align to support book bans on a case-by-case basis, preserving intellectual freedom, and age-appropriateness, and addressing (parental, educator, etc.) concerns through open communication and alternative options rather than outright censorship. Examples... parental emails on books accessed, lib policy for parent permission to access targeted books, alternative assignments, etc.
-------
@ThreePointTakedown seemed to agree with you initially, but later his statement: "I agree with parents in Cali. Well done." might support the parent's behavior to influence "Flamer" removal from the K-6 library. (article link)
Have you been able to read into that situation? Is Flamer appropriate for K-6 school libraries?