Not entirely, in this context. If the lady's behavior is otherwise notorious and/or unrepentant, the school is not required to "forgive" her to the point of maintaining an association with her.
As I've said, I suspect (without real proof) that the school is behaving poorly, and that the woman is well shut of them. So on that point, we agree.
They are entitled to judge and disassociate themselves from such folks. I doubt she was though, and wouldn't have been teaching the kids that sex outside of marriage was fine.