Now, now. Few Catholics are priests. Most are members of families, with (married) mother and father and their joint biological children. Most families are of modest size. Somehow or other, and despite church teachings, they match their family size to their means. And Catholic schools get generally better outcomes with less input than the public schools. You can put that down to Catholics being brighter if you wish, but maybe it has more to do with how there's order in the classroom and parental backing for the teachers.