The now famous praying American football coach wants his job back.

Joe Kennedy, the assistant football coach of Bremerton High School in Washington state, is taking the Bremerton school district to court, saying it violated his religious rights when they fired him from his job for praying on the field after games, the Daily Mail reports.

The lawsuit was filed on Tuesday at the U.S. District Court in Tacoma by the First Liberty Institute, a Texas-based legal organisation that focuses on religious freedom cases.

The lawsuit wants the court to order the school district to give Kennedy back his coaching job and to allow his post-game prayers.

Kennedy said he was "devastated" when the school district fired him in November last year.

"I really hope that the school district will give me my job back so I can get back to doing what I love most: coaching my players," he said.

Before he was terminated, Kennedy had been praying before and after games, sometimes joined by students, since 2008.

The Bremerton School District said they first warned Kennedy to stop praying since they did not want to be seen as endorsing religious activity.

However, Kennedy continued praying silently by taking a knee, drawing national attention and forcing the school district to fire him.

The lawsuit defended Kennedy's action, saying he "is not motivated to engage in private religious expression in order to proselytize or attract others to his religious faith."

"Instead, he offers a brief prayer of thanksgiving as part of a covenant he made with God before he started coaching at BHS," it said.

Kennedy's prayers were about the players, their hard work and sportsmanship, the lawsuit said.

First Liberty Institute insisted that the school district misinterpreted prior court rulings concerning the religious rights of public employees.

The legal organisation also questioned why the school district did not take action against another football coach who performed a Buddhist chant at the 50-yard line after games.

The school's "blanket ban on any demonstrative religious expression by Coach Kennedy violates the First Amendment, as does its decision to take adverse employment action against him because of such expression," the lawsuit said.