If Congress passed legislation mandating all high schools to pray before football games, that would be unconstitutional.
If a community chooses to express their religious beliefs publicly, it's not unconstitutional.
I've been to high school games where they allow a local pastor or chaplain a few moments to say a brief prayer. No one is forced to pray, no one is condemned for not praying. It simply happens and it's over.
I believe very strongly in freedom of expression. Silencing the majority simply because a handful of people disagree is wrong.
It doesn't matter if it was a Muslim prayer, Jewish prayer, Hindu prayer, Wiccan prayer, or whatever. Preventing freedom of expression simply because one or two people may be uncomfortable for a moment is wrong.