A case involving a St. Paul teacher who sued the district after he was attacked by a Central High student in December 2015 is nearing a critical moment in U.S. District Court.

John Ekblad has accused former Superintendent Valeria Silva and her administration of failing to crack down on assaultive behavior in the schools, specifically by black students.

"The school district created and perpetuated an environment, through its rules, which ultimately led to a culture of violence," Ekblad's attorneys contend in court documents filed Friday.

The filing came in response to a district request that Ekblad's case be tossed before it goes to trial. The district's attorneys argue that employees who seek remedies for job-related injuries must do so through the state's workers' compensation system, and not the courts. They also say that Silva and Theresa Battle, an assistant superintendent overseeing high schools, should not be held liable for Ekblad's injuries.

A hearing on the district's motion is set for May 4.

The attack on Ekblad marked a serious turn for Silva as superintendent because it came after her administration had been accused for several years of taking a lax approach to discipline and because it triggered a threat by teachers to go on strike if the district did not take action to make schools safer.

In its move for dismissal, the district noted last month that Ekblad had signed and cashed workers' compensation checks totaling $65,772 through March 3, and received medical benefits in the amount of $26,938. It also challenged Ekblad's claim that the district knew the student was a danger to others before the Dec. 4, 2015, incident.

Ekblad, a physical science teacher then earning extra pay as a lunchroom supervisor, was injured while trying to break up a fight in the cafeteria between a freshman and a senior.

According to authorities, the freshman's older brother grabbed Ekblad in a chokehold and slammed him into a table and chair, and then the floor, knocking him unconscious for 10 to 20 seconds. Ekblad reportedly sustained a concussion. About a month later, the teenager pleaded guilty to felony assault and was sentenced to 90 days of intensive supervised probation and electronic home monitoring.

The district contends that Ekblad faced the "special hazard" of dealing with and breaking up fights as a paid lunchroom supervisor and also as a member of Central High's safety team. He had no prior contact with the 16-year-old, and the district had no record of the student being violent in the past, the district said.

Ekblad's attorneys say that questions can be raised as to whether the student, who is black, attacked Ekblad, who is white, for racial or personal reasons — in turn qualifying it for the court's consideration.

The district knew it had a problem with assaults between students and teachers, but took no action to protect teachers, they argue.

They also revived an argument often made by a former teacher, Aaron Benner, who is black, that district leaders concerned about the disproportionate percentage of black students being disciplined were, in turn, failing to hold many of them accountable for misbehaving.

"Teacher after teacher stated that Ekblad's injuries were caused because administration treated African-American students differently when imposing discipline for fighting," Ekblad's attorneys allege. "The rule of treating students equally was not enforced, and as a result, Ekblad was in fact injured."

Benner gave a deposition in the case, but a transcript of his comments is not public.

The district has 14 days to respond in writing to Friday's arguments.