Seems to me that it's always people with a good Catholic school nearby that are the ones bellyaching about the system. I'm Catholic, I go to Mass every Sunday. I want my children to have a Catholic education, like I did. DD will go to the Catholic school in the town. Two roads away there is a state of the art, all mod cons, brand new primary school with lots of outside space and a fantastic reputation, despite its newness. DD can't go there because it's not Catholic. Whinge whinge whinge. I demand that she is able to go there and be taught the religion that we follow, even though it's not a Catholic school. Oh wait, only protestants can demand that.
Your Catholic school isn't at the expense of other schools, it runs alongside them, like every school in the area does. Your children aren't right for it. Tough tits.
You're not Catholic, so don't worry about the Catholic schools. Simple as that.