A federal judge Thursday dismissed a lawsuit brought by a St. Paul Central High School science teacher whose career ended when a student body-slammed him in December 2015.

The teacher, John Ekblad, sued former superintendent Valeria Silva and assistant superintendent Theresa Battle in March in U.S. District Court, accusing them of failing to protect him.

Lawyers for the school officials asked to have the case dismissed, arguing that under state law, Ekblad must go through the workers compensation system. U.S. District Judge David Doty agreed, finding that no exceptions exist that would enable Ekblad to sue.

“Obviously, we’re disappointed. We felt we had a strong case,” said Phil Villaume, Ekblad’s attorney.

Villaume said they will appeal the ruling.

“This decision affects every teacher in the state of Minnesota,” he said.

Minnesota workers compensation laws have been described as a compromise: They protect employers from costly lawsuits while compensating employees for workplace injuries, even when the employer was not at fault. In most cases, the system is the “exclusive remedy” for workers hurt while on the job.

But Villaume argued as many as three exceptions apply in this case that would enable Ekblad to sue.

ASSAULT EXCEPTION

The assault exception is for cases where the employee was injured for personal reasons unrelated to his employment. Villaume said this was their strongest argument.

He argued the student, who is black, assaulted Ekblad because he is white. He also argued Ekblad’s job duties did not require him to put himself in harm’s way.

Doty disagreed, partly because Ekblad received extra pay as a lunchroom supervisor. Ekblad was not obligated to break up the lunchroom fight, but he acted within the scope of his employment when he chose to do so, the judge found.

“Ekblad, a school district employee paid to maintain order and safety in the lunchroom, intervened in the fight in the course of his duties. Under these circumstances, his injuries arose from circumstances directly related to his employment,” Doty wrote.

INTENTIONAL ACT EXCEPTION

For the intentional act exception to apply, Villaume needed to demonstrate that Silva and Battle were not simply negligent but had a “conscious and deliberate intent” to harm Ekblad.

Villaume’s claims — that Ekblad was injured because of school district policies and decisions that gave black students preferential treatment for discipline — “do not establish that (Silva and Battle) consciously and deliberately intended to inflict injury,” Doty wrote.

CO-EMPLOYEE LIABILITY EXCEPTION

The co-employee liability exception is for cases where an employee displayed gross negligence by breaching her duties to a fellow worker.

“Even assuming Silva and Battle are Ekblad’s co-employees, the incident did not arise from negligence directed toward Ekblad or tortious conduct in which they participated, nor did it occur at their direction,” Doty wrote.

FULLY DISABLED

Ekblad, 56, has not returned to his job since the attack. He said after a court hearing this month that he thinks his career is over.

He cited ongoing memory and hearing loss, headaches, tremors and a burning sensation in his foot and said he no longer handles stress the way he used to. He’s now receiving full disability payments from Social Security, he said.

The school district said in a March court filing that it had paid Ekblad $65,772 in workers compensation since the attack, as well as tens of thousands in medical benefits.

“Saint Paul Public Schools does not condone violence under any circumstance and has always made safety a top priority for its students and staff,” the district said in a prepared statement Thursday.

“The dismissal of the lawsuit allows the workers’ comp system to operate as it was set up to do — compensate staff who are injured while at work.”

The 16-year-old student who injured Ekblad pleaded guilty to third-degree felony assault and was given 90 days of home monitoring and community service. He told a judge he was trying to stop a fight involving his younger brother when Ekblad grabbed him from behind.