All those things you have written are true Suzie but none of them set one religions teaching's above another. If a teacher, for the sake or argument, shows a class a cartoon that one specific religion finds inherently offensive, then that teacher is automatically setting one religion's standards above another's by saying we need to look at this, even though you find it blasphemous, because our liberal western values say it's OK.
And I don't believe that any school has any right to undermine what a child's parents have given them as a belief system, however we disagree with it. And if anyone in any school had led me to believe that their belief system was better than mine, that would have been wrong. So it has to work both ways.
I'm afraid that I believe that religious beliefs are not even "a little add on" to understanding society and have no place in education.