Clearly, there are people who do not want to leave their sin. But do we give up? I have heard statistics that people have to hear the gospel an average of seven times before they accept it.
Oh, and thank the Lord that people did not give up on me when I was in the pit of hell, doing things that I am not proud of. My sin was never winked at, but longsuffering people recognized that I was still a person who needed Christ and was at least willing to associate with people who knew Him as Savior.
I am the first person who is completely blown away by the Grace of God. Can you point me scripturally where Jesus approached someone 7 times and asked them to go and sin no more? His message hasn't changed from generation to generation.
The one person (the rich man) who explained why he couldn't follow 'right now' never made the choice.
I'm not saying it's right to call people ugly names or throw them away. But I believe it's a mistake to misrepresent or misconstrue how Jesus approached sin and redemption. Paul was pretty harsh about it too.
When someone outside of the Christian Faith tries to manipulate Biblical principles (like these two women) it needs to be addressed, quickly and with grace and calm. If the situation changed, I'm sure the school would take the girl back on at least a probationary period.
I think that parents that send their kids to Christian Schools (or homeschool) get to decide as a family when and how to approach things that are outside of a Biblical family unit, not have it thrust on them by a couple with an agenda.