"...engage in practices "immoral or inconsistent with a positive Christian life style"
I'll congratulate them if you can show where they forbid children of divorced parents or worse, children who's parents have divorced and remarried. Until then it sounds like another case of selective morality to me.
How is it possible for lesbian parents to "go and sin no more"?
If you don't think for a second these "parents" didn't enroll this child for political purposes then you're selectively arrogant. Why exactly would members of the Film Actors Guild enroll "their" kid in a school that will teach that their parents are immoral, because the parents are trying to repent? Not only are they using "their" child for some sick political stunt they're also involving the other children at that school all in the name of justifying their selfish perversion.
There are Biblical allowances for divorce. In the instance of infidelity, for example.