Walking out to the 50-yard line to pray amounts to not much more than a self-aggrandizing stunt.
He holds power over his players.
It is not unreasonable for them to assume that if they don't join their coach, their playing time could be adversely affected.

Praying in public falls under Free Speech.
However, the "faithful" are required to adhere to civil laws. They must be prohibited from using their positions as public servants to proselytize to students, or anyone else, while doing their jobs.

That's my story and I'm sticking to it.

From the article: "In fact, Jesus warned against showy public prayers, saying in the Gosel of Matthew that hypocrites love to pray publicly “that they may be seen of men.” God’s rewards, according to Jesus, flow to those who obey his command, “When thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father.”"

Christianity as it is actually practiced sees bullying as a mainstay of their behavior. That SCOTUS would even give this case a hearing plainly demonstrates the hypocrisy of mainstream Christianity and the corruption of SCOTUS by Fake americans (Putin-americans).