The North Branch School District failed to prevent a sexual assault of a special education student on a school bus, according to a lawsuit the boy’s mother filed in federal court last week.

In April 2013, the 6-year-old student, referred to in the suit as Jr. Doe, was escorted onto the bus by a district employee. The boy went to the back of the bus, where a middle school student was seated, the suit said.

Both the district employee and the bus driver had been warned that the middle school student had a history of engaging in sexually inappropriate touching of young children, the suit said. The district was told that he was to have absolutely no unsupervised contact with children under 10, the suit said.

Both students were regular riders on the bus. The district employee sat in the front of the bus with the driver, the two talking to each other, facing forward and ignoring the students, the suit said.

About 10 minutes after Jr. Doe boarded the bus, he was sexually assaulted by the middle school student, the suit said. Eventually the bus driver glanced in her rearview mirror and saw Jr. Doe being assaulted. She stopped the bus and moved the middle school student to a front seat.

“Minnesota parents and their children have the legal right to be safe and free from dangers created by schools,” said Andrew Muller and John Klassen, the attorneys representing the boy’s mother. “In this case, North Branch utterly failed to protect a 6-year-old special education student from such a danger — a sexually dangerous older student who the school district and its staff knew presented a risk of harm to other students. The district and its employees have caused the victim and his family irreparable harm.”

North Branch Superintendent Deb Henton said Tuesday that she hadn’t seen the lawsuit and couldn’t comment. She would not say if either employee involved in the incident has been disciplined or fired.

A week after the incident, the state Department of Education received notice of it. It investigated and sent a copy of its report to the district. No details of that report were provided in the suit.

The district and the North Branch police also investigated and prepared their own reports, the suit said.

The suit asks for damages in excess of $100,000 for each of five alleged claims of violations by the district and its two employees.

David Chanen 612-673-4465