Gee, I don't know. Maybe they thought it was a good school and they appreciated the disciplined environment? The usual reasons why anyone chooses a private school.
Ignore the fact that this is a religious or a christian school and a basic fact still remains this school requires it's students to be from conventional and well adjusted families.
Define conventional and well adjusted. The two women had been together for over 20 years. How many of the heterosexual parents can say that? Is a single parent family conventional? How do they determine how many of the families are well adjusted? Do they have to take a test or submit to inspections?
That's the bottom line, you want to go to school here, you obey our rules and requirements.
Which they did, until their kid was kicked out. Let's not kid ourselves that it was for anything other than the fact that the parents were homosexuals and the school has a selective sense of what is moral and what is not. They could have been a married couple where the father was abusive and the mother was a drunk and the school would have accepted their tuition.
They didn't obey the rules of the school in the first place.