Removing any financial incentives to get married would also be a positive step.
I definitely agree with this.
"Their house, their rules" is an important principle. It would actually be imposing (and hard to enforce) if you forced schools to not discriminate. However, it is to the detriment of catholic schools that they choose to discriminate: they are left with less choice. You might accuse me of being unfair to the homosexual teacher, but there is no better alternative. Forcing a school to view homosexual teachers objectively is not practical, nor is it fair for the school - who own the property and should be able to manage the school the way they wish. On the other hand, the lower demand (since some catholic schools will not demand them) for homosexual teachers will make them cheaper for other schools to hire them - helps the parents.
Keep in mind that even though I am against outlawing discrimination, I am certainly not against individual choices against discrimination. The bad publicity the school gets from media sensationalisation ("discrimination scandal!") is the price they pay.