What do you think about religion-centered student groups in public high schools?

The discussion that has recently arisen in this thread inspired this question. Do you think it’s okay for public high schools to have religion-centered student groups? If so, how about atheism-centered student groups?

My high school had a group called the Fellowship of Christian Athletes, which I always thought was kind of bizarre. I’m not sure I understand the purpose of gathering Christian athletes in a high school group, as opposed to simply athletes.