BREMERTON, Washington — A coach’s personal act of prayer that grew into a public spectacle after Bremerton High School football games is now a major test of the First Amendment in a case Monday before the U.S. Supreme Court.

The coach, Joe Kennedy, who was suspended by the school in 2015 over post-game prayers on the field, is asking the justices to affirm the right of public school employees to pray aloud while on the job, even when within view of students they coach or teach.

“This is a right for everybody. It doesn’t matter if you’re this religion or that religion or have no faith whatsoever,” Kennedy told ABC News . “Everybody has the same rights in America.”

The school district says Kennedy’s prayers, some of which were surrounded by players at the 50 yard-line, are hardly private acts of faith and run afoul of constitutional prohibitions against promotion of religion by government officials.

“It was my covenant between me and God that after every game, win or lose, I’m going to do it right there on the field of battle,” Kennedy said of his ritual, which he said typically lasted less than a minute.

Lower courts sided with the school district. A Supreme Court ruling for Kennedy has the potential to expand the ability of public school employees nationwide to practice their faiths more openly around students, legal experts say.

The case being argued Monday will be decided by the end of June.

The First Amendment protects free speech and free exercise of religion, but it also prohibits the establishment of religion by the government. The Supreme Court has long said that public school-sponsored prayer violates the Establishment Clause, even if the prayer is voluntary.

It has struck down Bible readings and teacher-led prayer in classrooms, religious invocations at graduations and religious displays at other school sponsored activities. In a 2000 case, Santa Fe Independent School District v. Doe, the court said that opening football games with student-led prayer is also unconstitutional.

At the same time, the court has ruled that free speech rights don’t end at the schoolhouse gate and that religion need not be entirely expunged from public schools.

While Kennedy routinely prayed on the field after games for more than seven years, attracting varying levels of participation from students, it wasn’t until 2015 that the school district informed him that separation of church and state meant he could no longer pray with players and keep his job.

“They just said if anybody could see you anywhere here, it was over,” Kennedy said.

The school district explained at the time that the prayers violated “constitutionally-required directives that he refrain from engaging in overt, public religious displays on the football field while on duty.”

Some Bremerton High School parents like Paul Peterson, whose son Aaron played for coach Kennedy in 2010, later complained the prayer sessions were applying inappropriate pressure.

“The coach is a leader. The coach is a mentor. If he goes to the 50-yard line, he has a message he wants to deliver, and so the players would follow,” said Peterson in an interview.

“The harm is to those who are the minority students, the minority faiths, the students who have no faith,” he said. “They are being pressured into doing something that they don’t fundamentally agree with.That’s what the First Amendment protects us from.”

Kennedy insists there was no coercion, though widely publicized scenes show his post-game prayers became much more than solitary acts of faith.

Attorney Jeremy Dys, representing Kennedy on behalf of the First Liberty Institute, said the coach should not be held accountable for the voluntary decisions of others to join him in an expression of faith.

“He’s not on the field coaching anybody, he’s not telling what play to run. No instruction taking place,” Dys said. “School districts don’t own every word out of your mouth or any religious expression that you choose to make in your private time, even on school grounds.”

A federal appeals court called Kennedy’s characterization of his prayers as brief, quiet and solitary as a “deceitful narrative,” noting that they were clearly audible prayers surrounded by groups of students, amounting to unlawful religious speech as “a school official.”

“If this were a case about a coach who in fact wanted to pray privately, in a solitary manner, we wouldn’t be here,” said Rachel Laser, executive director of Americans United for Separation of Church and State, a nonprofit advocacy group backing the school district. “You don’t leave that behind when you go teach or coach at a public school, but what you do leave behind is your ability to engage students who are very impressionable, who are required to attend public school.

Kennedy’s case has been cheered on by top Republicans, including former President Donald Trump, dozens of state and federal lawmakers, and star NFL quarterbacks, like Kirk Cousins and Nick Foles, who have told the justices in a friend-of-the-court filing that the power of prayer promotes good sportsmanship.

“These kids mean everything to me, because I was a troubled youth, and I wanted to reach out to help these kids in Bremerton, give back to my community which I terrorized as a kid,” said Kennedy, who is a Marine Corps veteran and former project manager at the Bremerton naval shipyard.

On the other side of the debate, leaders of minority faiths, atheists, and parents like Peterson, say a coach’s good intentions shouldn’t be an excuse for flouting the Constitution. The school district has received broad backing in court filings from professional athletes, members of Congress, civil rights groups, teachers unions, and local government groups, including the U.S. Conference of Mayors.

“When the teacher or coach is standing up and leading the children, I think you cross the line into indoctrination,” Peterson said.

The case could have an impact on public school playing fields nationwide and determine whether Kennedy can coach again, and take a knee in prayer for his Bremerton Knights.

He currently lives in Florida but has told the court he would move back to Bremerton if the justices rule in his favor.

“Nobody should have to be fired or worry about their job if they show any signs of faith,” Kennedy said. “At the end of the game, I’m hoping to have victory but we’ll see how the courts rule.”