An ex-con and math teacher at an elite Brooklyn private school who was once a candidate on “Jeopardy!” was arrested last week as part of an investigation into sexualized images being spread across social media, sources said.

Convicted thief Winston Nguyen — who served time in Rikers for stealing $300,000 from an elderly couple — was arrested at St. Ann’s School in Brooklyn Heights last Thursday in front of a crowd of students.

Nguyen wasn’t charged, but is being investigated by the Brooklyn District Attorney’s office, sources confirmed to The Post. He was released Saturday.

“We are awaiting a decision from the Brooklyn DAs office regarding charges against Mr Nguyen,” his lawyer, Frank Rothman, told The Post in an email.

“We are expecting some movement in the near future.”

A spokeswoman for Saint Ann’s — where high school tuition costs more than $60,000 per year — confirmed to the Daily Beast, which first reported on the story, that Winston “is a suspect in an ongoing investigation related to the dissemination of intimate images via social media.”

“Upon his arrest on Thursday he was immediately placed on leave by the school and he remains on leave,” the spokesperson noted.

The day of Nguyen’s arrest, Saint Ann’s Head of School Kenyatte Reid notified parents that the middle- and high-school mathematics educator had been arrested over an investigation that “dates back to January 2024.”

Reid did not reveal what the investigation involved until days later, when he told parents in a follow-up email that it related to “inappropriate sexualized images” and that Nguyen was barred from contacting anyone in the school community and from visiting the school, the Daily Beast reported.

“This incident is very disturbing to all of us,” Reid wrote “We pride ourselves on our amazing faculty and a learning environment rooted in trust.”

Nguyen has been teaching at St. Ann’s School since 2020 — just one year after he was sprung from Rikers Island for using an elderly couple as his personal piggy bank.

He pocketed more than $300,000 while working as the couple’s home health aide and used the cash to buy ballet tickets and a trip to Florida.

During his time in jail, Nguyen publicly blasted the Department of Corrections conditions, twice calling into a radio show to speak with Mayor Bill de Blasio, and later filing a lawsuit against the city.

St. Ann’s said it had conducted a comprehensive background check that includes criminal records during the hiring process.

“A nonviolent criminal record may not preclude employment,” the school spokesperson told The Daily Beast. “The school gives a careful and discerning assessment of a job candidate’s potential fit with the school.”

Nguyen did not respond to a request by The Post for comment.

St. Ann’s School is a renowned institution that boasts a laundry list of celebrity alumni and staffers.

“Girls” creator Lena Dunham, artist Jean-Michel Basquiat and Maya Hawk, the daughter of Ethan Hawke and Uma Thurman, are among the famous former students.

Tuition for the luxury school starts at $52,900 for preschoolers and rises to $60,525, plus a litany of additional fees, for high school students.