From some of the replies, I'm not sure which side of the issue they are on. But, maybe I am just slow.
Children are impressionable, which is why both religions and tyrants want to get to them early.
Prayer assumes a God, therefore it is a form of teaching religion. Most prayers are specific to particular religions, which is even worse.
Our laws require us to send our children to school, although if you have the means you can pick a private school or home school, thus giving you more say in what is taught. But if schools teach/approve/endorse a particular religion it is the poor working families that will have the fewest options. That bothers me, even if the religion is subscribed to by the majority of the community or the school board. We should not have a "state religion" even if it is the majority religion. I think the folks that originally wrote our constitution understood this, even if they did screw up on things like slavery and voting rights.
I think the place to teach religion is in the church/temple/mosque/forest/etc. where law does not require us to send our children.