I'm surprised that in this day and age that any school employee would be stupid enough to lead a group of students in prayer while on school property. Is the guy so incredibly ignorant that he's never heard of the Establishment Clause of the Constitution. Any disgruntled player or ex-player could easily turn this into a lawsuit with a high dollar price tag on it and any citizen in the community could also file a lawsuit although the damages would be significantly lower.
Our Constitution guarantees freedom of religion, but it also specifies that our government must remain neutral on matters of religion. It is in fact unconstitutional for public school athletic coaches to lead students in prayer and to conduct any religious activity around their students.
LINK: http://www.heraldnet.com/article/20151110/OPINION02/151119977