Two female basketball coaches turned a Catholic secondary school into Horndog High, bedding students for years under the watch of a skirt-chasing athletic director, according to an alleged victim and three school sources.

The NYPD says it’s now investigating sordid allegations swirling around Moore Catholic High School, a top Staten Island institution founded by nuns in 1962 and charging $8,000 in annual tuition.

Among the claims is that Megan Mahoney, a former assistant women’s basketball coach and gym teacher, had a months-long sexual relationship last year with a 16-year-old student; and that Richard Postiglione, Moore’s athletic director and chief operating officer, failed to report multiple faculty-student affairs to authorities beginning as early as 2006, though he and the principal were told of the randy romps.

The most recent alleged victim, whose name is being withheld by The Post, said he and Mahoney engaged in multiple trysts in her car, beginning last fall after she approached him in the gym and offered to coach him in basketball.

We would just drive around and [do it] in the car. - 16-year-old student

Mahoney, 25, who was also the assistant athletic director at the 450-student school in the Bulls Head section, would pick him up and take him to secluded spots to have sex, the boy said.

“We would just drive around and [do it] in the car,” he said.

He said the two never talked about the illegal or inappropriate nature of their relationship. “That never came up,” he said.

“We were never boyfriend-girlfriend,” he said. “It was cool. I knew it wasn’t going anywhere. I told my best friend and like three kids.”

Their reactions?

“How awesome — good job,” he said.

Mahoney denied having sex with the student.

But the teen’s parents said they saw them together, including one evening when the coach picked him up at their home for what they assumed was a date.

They believed Mahoney, a stunning former hoops star at Wagner College, was a high school student herself.

“She looks young,” said the father. “You’d never know.”

Postiglione was told about the sexcapades, according to two school sources.

“Richie knew all about it,” said one source, who learned of the relationship from the teen’s close friend and informed principal Bob Manisero. “Bob told me [Postiglione] had investigated and there was no truth to it. He told me she came from an upstanding Catholic family. But there was notorious gossip all over the school. These boys didn’t keep quiet.”

In December, the source emailed Postiglione and school board chairman Anthony Ferreri about this “serious issue.”

“If you remember I had report[ed] some activity some time ago about a basketball coach that I had learned,” the Dec. 19, 2013, email reads. “Rich thought it was untrue even though I knew it was correct … I was told they are in LOVE … Hope you have followed legal protocol to report even when there is no witness.”

A second school source said that Postiglione, Manisero and Ferreri were all informed but did not tell police or child-protection authorities.

“Bob said, ‘I heard it from the kids, but if you listen to everything they say, you’d go crazy,’” the source said.

Instead, the school sources said, Postiglione confronted Mahoney and made her promise to end the relationship.

But in January, the illicit lovers were spotted having dinner together at a pizzeria. A 911 call was made by the teen’s jealous ex-girlfriend, who had been following the pair, the boy said, and cops showed up.

“I told the officer, ‘I’m with my cousin,’” he said.

Mahoney resigned under pressure later that month, the school sources said.

The student says he was then subjected to retaliation by his teachers and faculty. “They were looking to fail me,” he claimed.

His mother agreed. “They wanted to get rid of my son, get him out of the school.”

She expressed her concerns in an email in April to the New York Archdiocese, complaining that a probe had been conducted without her knowledge and that her son was being drummed out of the school. She got no reply, she says.

Ferreri initially told The Post that Moore informed the city Administration for Children’s Services about Mahoney and the teen. He then backtracked and said the matter was handled by the Archdiocese, which did not contact ACS.

The boy’s mother said a caseworker came to their home in June — but only to investigate an unfit-parenting complaint filed by Moore. “I told her about my son and the teacher,” said the mother. “She had no idea.”

The complaint against the parents was dismissed as unfounded.

A source familiar with the investigation backed the mother’s account, saying ACS did not learn of the allegations until June following the site visit.

ACS declined to comment, citing privacy laws.

The Archdiocese said it reported the matter to the Staten Island DA’s office when it “learned of these allegations.”

The DA’s office declined to comment.

The school sources claimed Mahoney bedded another 16-year-old boy in 2012, but nothing was done about that relationship.

Around 2006 or 2007, they said, another female coach under Postiglione was reported sleeping with a female student.

“Rich knew about it in the first year and let it continue for four more years,” the source said. He forced the coach to sign “an agreement … to stop.”

But the relationship continued and the coach eventually resigned under pressure, the school sources said.

Ferreri said the claim that Mahoney had sex with another student was “unsubstantiated,” and that no allegations were ever raised against the first coach.

Postiglione and Manisero did not return calls to their cellphones.

The married Postiglione, 57, allegedly tried to get in on the sexual free-for-all, attempting to seduce Sabrina Panfilo, the former development director at Moore — touching her buttocks and insisting that she sit on his lap, according to a complaint Panfilo filed with the state.

[Postiglione] told [Panfilo] that she had ‘a dancer’s body,’ they were ‘soul mates’ and he was in love with her…

He told her that she had “a dancer’s body,” they were “soul mates” and he was in love with her, and he once barged into her office, slammed his hands on her desk, and said, “Let’s have an affair,” according to Panfilo’s complaint to the Division of Human Rights.

While proposing a romantic getaway, Postiglione offered that Panfilo’s infant son could be watched by Mahoney, “a woman who has been alleged to have engaged in sexual relations with a minor at the school,” the complaint says.

Panfilo told The Post she was fired in “retaliation because I rejected his sexual advances and made a formal complaint to the board.”

The Archdiocese said it was aware of Panfilo’s complaint and pledged to “cooperate in any way that it can with helping to bring this matter to a proper resolution.” It is also conducting a “forensic audit” of the school’s books, which are handled by Postiglione.

The school sources said they were concerned about an arrangement Postiglione made with a car-service firm to take him to the school from his home in New Jersey in 2007, when he was arrested for reckless driving and refusing to take a breath test. His driver’s license was suspended for 210 days, New Jersey officials confirmed.