Ok with me as long as she knew the policy going in, and the same standard applies to unwed fathers.
I'm fairly certain this school's policy was in place long before she was hired. It's a Christian School, think New Testament...
Whatever the legal consequence, this school should be commended for adhering to its Christian doctrine over secular, legal doctrine. And I'm sure the Congregation is happy to have her out of their midst and away from their children.
R3