No one's is judging the Christianity of the child. The school is acting based on the agreement between the school and the 'parents' who signed her up to go. It's a private school.
Would you, in your righteous Christian fury
Post where I ever made a comment that even implied 'Christian fury'. You won't be able to.
Would you deny Christian children with a Christian father access to His Word because their mother happens to be a sinner?
Post where anyone said that the girl could not pick up a bible and read it. You won't be able to.
The Bible is the only guide that should be used when evaluating matters of faith, and the Bible tells me that the actions of this school were wrong.
This isn't a 'matter of faith,' it is a matter of a private school having rules that were agreed upon by the 'parents' and subsequently violated. Post the verse from the bible that says an agreement should not be enforced and you might have a point. But of course, you won't be able to.
The people running this school are the real life Pharisees of our day
No, the people running this school are taking very seriously their duty to ensure a Christian environment for ALL their students, not just this one girl. Apparently, they have put that term into their agreements because of past experiences with children whose parents are homosexuals. If the 'parents' of this child did not want to abide by those rules, they could have easily picked a different school.
If you are so passionate that someone needs to 'school' this child in a Christian environment, you could offer to home school her yourself, or to help them find another school that does not have those rules, or to open one yourself that doesn't have such rules. But no, you'd rather demand that someone else do what you say instead of you doing it yourself. (Speaking of Pharisees. . . )