I think it's a real shame that they did this. The woman slipped up and didn't abort her baby to hide the fact that she did have sexual intercourse before her marriage, while she was engaged. The school decided to confront her about that and nitpick the rules as an excuse to fire her. I think they did it because it's a pain in the ass to grant maternity leave. I think they are hypocrites and I hope the PR backlash from this hurts them. They are poor excuses for Christians. I'll bet most of the people working there have fornicated at one time or another.
So yes, the school probably has the right to use their moral clause as an excuse to can someone, but that doesn't make it right.