Debate in the Catholic community in Australia often centres on how the Catholic school best expresses its Catholic identity. Is it in closing its doors to all but Catholic families or does Catholic identity require an openness to all Christians, those of other religions and those of no religion? This paper argues that if the school is to be truly Catholic, it must possess and display the unity of the Church itself, and, paradoxically, this unity calls it to openness to all. This openness is not in conflict with a healthy Catholic identity, but is a constitutive aspect of this identity, just as important in the work of the Catholic school as the linking Catholic children and young people with their local Catholic church structures. (Contains 2 notes.)