Why prayer shouldn't be allowed in school?

I am doing a research paper at my Christian school on "Why pray should not be allowed in the public schools" ... I need 3 good sources on why pray should not be allowed in public schools, to an extent. I know it should not be allowed to extent, because they have a right to pray in silence to whatever god they believe in, but the teachers should not pray allowed to the children. Like if the teacher was a devil worshiper, that would be a problem to any child who didn't believe in that. So I need 3 sources basically saying that the school prayer is good just the way it is now.