Don’t be late returning books to this Bronx high-school library.

Students last week spread around social media a photo of the Taft Educational Campus chief librarian holding an assault rifle inside a gun shop.

One student at the Claremont school reposted the picture of Elizabeth Ervin, 47, with the snarky caption: “Don’t return the books in the library and you’ll see. Only ppl [sic] from Taft understand.”

A friend of Ervin’s said the photo, taken two years ago on her birthday, was “stolen” from her Facebook page and that she is the victim of cyber-bullying.

The city Department of Education’s social-media policy requires teachers to keep their personal social-media pages off-limits to students.

Kids at the Taft campus — which houses six high schools — cracked jokes about the photo of Ervin smiling as she gripped the huge firearm.

“Everyone in Taft looking for those books now,” quipped a student.

Many students found it funny.

“When my friends and I saw it, we all started laughing” said a freshman at the Bronx HS of Medical Science.

But others were alarmed.

“It makes me feel insecure and uncomfortable. Teachers shouldn’t have guns,” said a freshman at the Bronx Collegiate Academy.

A Taft staffer alerted to the photo by three kids was appalled by the picture, and called Ervin “disgusting.”

Ervin — who is also Taft’s athletic director — yanked the photo off Facebook and deleted her account. She did not return e-mails and phone calls seeking comment.

A city teacher since 2002, Ervin has a history of butting heads with colleagues but enjoys a close relationship with BCA Principal Darryl White, insiders told The Post.

“She can basically do whatever she wants and get away with it,” one griped.

Ervin made more than $90,000 in salary last year and an additional $31,678 in overtime pay, records show.

A spokesman for the Department of Education said the city’s Special Commissioner of Investigation will look into the incident.