I went to private school for the last three years of secondary school (up until age 16), and it was a christian (CoE) school (although neither me, nor my parents are christian). But this was in the UK, and the Christianity was never forced, just certain things were upheld (like saints days, church services and that). I have little experience of American Christianity, but I know that sort of thing would get stomped on over here quickly, if it happened at all.

I guess its all based on the school though.