A Long Island school superintendent was suspended after an investigation showed that he required all eighth graders in his district to enroll in a digital learning program — which his own company had created, officials said.

Michael Nagler, who was named New York state’s “Superintendent of the Year” in 2019, was found to have violated ethics rules by pushing the “Build Your Own Grade” program developed by Quave, a company he founded with his son James last July.

The board of the Mineola Union Free School District hired private eyes to look into the alleged conflict of interest.

Investigators found that Nagler had failed to disclose Quave’s for-profit status to the board before mandating the online grading app’s usage across the eighth grade — as trustees believed the system was created as an internal, voluntary project and not a private business venture.

“It never, ever crossed my mind to ask our superintendent if the volunteer service that his son was performing was going to be turned into a limited liability company with the intent of monetizing it,” board trustee Patrick Talty, told Newsday. 

Parents in the district raised concerns about the program, which was killed by the district in October while the investigation was underway.

Nathaniel Nichols, an attorney who investigated the case, said he interviewed 16 witnesses, including Nagler, and recently laid out his findings before dozens of parents and residents at a packed meeting in a high school auditorium.

Nagler eventually came clean to trustees that he had created the company, in part, to obtain tax write-offs and to protect his son’s intellectual property, Nichols confirmed to The Post.

Also, Nagler’s grading system was hosted outside the district’s control, raising concerns about the security of student data on a privately owned server that had never been formally approved, Nichols said.

Nagler, who has worked in Mineola since 1999 and has served as superintendent since 2009, was suspended last Thursday. He could not be reached for comment.

The superintendent will remain on paid leave until the board’s next meeting on Jan. 22, while trustees review the investigation’s findings.