I like "Imagine" and enjoy singing it in some contexts, but I wouldn't do it in a public performance in a religious school. I'd do it in a classroom as a springboard for discussion, but not in a school assembly or in a performance for parents or the public.

I also like "Onward Christian Soldiers" because it's an interesting song - but I wouldn't choose it for a religious service because I think religions need to get away from the imagery of warfare. Religions fight too damn much, even though most of them profess to believe in peace.

-Joe-