A Long Island music teacher who once worked for a local school district and the popular School of Rock program was busted this week — trying to meet a 13-year-old boy at a hotel for sex, authorities said.

Charles Bull, a 53-year-old former teaching assistant at the Locust Valley School District, was scouring a chatroom called “LongIslandDLMenOnly” on the social media app Kik when he came across a post from an undercover cop posing as a dad with his son.

The officer had posted that he was “on vacation with his son…and looking for things to do,” according to the criminal complaint.

Bull — using the screen name “Charlie Blue” — messaged him back “express[ing] interest in pursuing sexual activities with the son,” the complaint states.

The two men met in a coffee shop in Farmingdale on Tuesday, where they initiated a 3-way Kik chat with the purported son, whom the “father” claimed to have holed up at a nearby hotel.

The next day, Bull arrived at the hotel carrying three unopened condoms — and an Xbox video game gift card. The feds busted in and arrested him, according to the complaint, and Bull wound up confessing to everything.

“I’m not going to lie. I was there to have sex with the 13-year-old boy,” he allegedly told cops.

“I know it was wrong, and I can’t hide that.”

Bull worked for Locust Valley this past year and had also spent time educating kids for the School of Rock music program, authorities said.

Attempts to reach the school district and program officials were unsuccessful on Thursday night.