Well, there you have it. Seems to me that the school was completely in their rights. Again, as someone said earlier, I hope that the school doesn't have to defend itself in a lawsuit or can get some free legal help.
Since the one 'parent' always came to school functions and the other 'parent' didn't, doesn't that strike you as an attempt to hide something?
As an aside, I wonder just what it was that the little darling said during the football game? Being at a Christian school is a privilege, not a right.
I fully understand 'hate the sin, love the sinner.' But the consequences of lying need to be addressed. It would be a much different deal if the two women came to the school and were open about their lifestyle and asked if their daughter could attend. If it were me, I would use such as an opportunity to share Christ. But if someone had signed an agreement and willingly deceived me -- and I think that most gay people know that 95% of Christians are not wild about the gay lifestyle -- then I would enforce the code.