I think in the education system there should be a clear separation between church and the state so I think it's unnecessary to be declaring religious affiliations, I think it just ends up offending people of different religions if everyone is proclaiming one religion or another, I think we are better off keeping it a secret.
I do not believe religious affiliations are public information. I believe people should maintain the right to name their religious affiliations. In some situations people may not feel comfortable giving the public this information and I feel that is justifiable. People form opinions, often falsely, about people when they know their religious affiliations.
I don't really see the relevancy of exposing one's religious affiliations in a classroom setting. Unless, that is, the class is about religion. The extreme of keeping it a secret seems to be rather ridiculous, in my opinion, it's just not relevant and doesn't need to be brought up. I was taught that one never talked about religion or politics in polite company.
Religious affiliations are a matter of personal choice, and should be kept out of the classroom environment. Disclosing religious affiliations would allow others to focus in on that aspect of your life as an explanation for why you think the way you do, sort of like pigeon holing you into positions that you may not even accept. Most ideas can be discussed without reference to a person's private religious beliefs, and they are best handled in this way in a classroom.
It is my opinion that religious affiliation has no place in a classroom. That type of information can have no positive affect on the education of a group of young minds, and would serve as only another means by which the student population can be divided. Not releasing this information would support unity.
This changes if you are speaking of students or teachers. Teachers should keep their orientation to themselves, or at least be required to point out that people simply have different perspectives.
Students should have individual freedom of expression. Getting into arguments over religious affiliation should be avoided, as it gets in the way of learning, but they are singular individuals, with individual rights that we shouldn't tromp on. They don't have authority over each other, so there is no conflict the way there would be as a teacher.