They don’t call him the Joker for nothin’.

The Joker costume-wearing 14-year-old arrested at his Queens school Thursday for threatening to “kill people after school” will not be charged — because cops determined his threats were all a hoax, police said.

The teen allegedly told staffers at the High School for Arts and Business in Corona “today would be a good day for a shooting,” before asking if the campus windows were bulletproof.

That prompted cops to nab the kid — whose Halloween costume paid homage to the controversial new “Joker” flick starring Joaquin Phoenix — around 1:40 p.m. and take him to Elmhurst Hospital Center for a psychological evaluation.

After an investigation, cops determined the threats were a hoax and decided not the charge the youth, officials said.

Students said they were shocked and scared about the incident.

“Thank god nothing happened,” said 14-year-old sophomore Semaje W. “It’s scary to think a student would find it funny to say things like that.”

Andrew Lima, a 15-year-old sophomore, said the incident was “crazy.”

“Today’s Halloween, so maybe he was just trying to get attention,” Lima mused. “If he got arrested … then he got what he wanted, attention.”

In a statement, the DOE confirmed there is no credible threat.

“Safety always comes first, and we are providing additional support to the school community. There is no credible threat, and all students and staff are safe,” a rep said.

Additional reporting by Israel Salas-Rodriguez and Tamar Lapin