A Robbinsdale school district teacher allegedly sexually assaulted two boys he was related to "well over 100 times" for several years, according to charges filed Thursday.

Matthew A. Bertsch, 28, of Richfield was charged in Hennepin County District Court with two counts of second-degree criminal sexual conduct and one count of producing pornography with a minor in connection with numerous incidents of abuse.

Bertsch was arrested Tuesday at the FAIR School in Crystal and jailed in lieu of $300,000 bail. He is due in court Friday, and records do not list an attorney for him.

Bertsch is assigned for the coming academic year to the FAIR School, which serves fifth- through eighth-graders , said district spokeswoman Toya Stewart Downey. As of Thursday afternoon, his employment status with the district had not changed, she said.

After Bertsch's on-campus arrest, Stewart Downey said in a statement that Robbinsdale staff "are focusing on what is most important at this time — welcoming students and families back to school beginning next week."

According to the charges:

On Aug. 3, a man went to police headquarters in Bloomington with his two sons, both young adults, and reported that Bertsch had abused the two as children for many years. They said the abuse started when one was 10 and the other 11, and lasted well into their teens. It happened most often in the basement of the father's Bloomington home, but also elsewhere, he said.

"All the incidents that we know of took place in Bloomington," said Police Chief Booker Hodges.

One of the young men "estimated there were over 100 instances of abuse," the charges read. "These instances occurred at multiple family homes. They would occur when there were family gatherings or when [Bertsch] was left in charge of supervising [the two boys]."

The abuse involved Bertsch exposing himself to the boys, fondling them and performing oral sex on them. Bertsch also showed them explicit videos and photos. One of the victims gave police a photo of Bertsch exposing himself.

Bertsch joined the Robbinsdale district last year and taught physical education at Plymouth Middle School. Before that, he was a substitute elementary teacher for Richfield Public Schools in late 2020 and early 2021, said district spokeswoman Jennifer Valley.

"Because we were in distance and hybrid learning during most of this time, he would have had limited contact with students," Valley said.

Bertsch earned a degree from Minnesota State University, Mankato, and was first licensed to teach in Minnesota in January 2019, according to state records.