18 Hence it is that in this proper object of her mission, that is, "in faith and morals, God Himself has made the Church sharer in the divine magisterium and, by a special privilege, granted her immunity from error; hence she is the mistress of men, supreme and absolutely sure, and she has inherent in herself an inviolable right to freedom in teaching.' By necessary consequence the Church is independent of any sort of earthly power as well in the origin as in the exercise of her mission as educator, not merely in regard to her proper end and object, but also in regard to the means necessary and suitable to attain that end. Hence with regard to every other kind of human learning and instruction, which is the common patrimony of individuals and society, the Church has an independent right to make use of it, and above all to decide what may help or harm Christian education. And this must be so, because the Church as a perfect society has an independent right to the means conducive to its end, and because every form of instruction, no less than every human action, has a necessary connection with man's last end, and therefore cannot be withdrawn from the dictates of the divine law, of which the Church is guardian, interpreter and infallible mistress.
Source: Divini Illius Magistri (Vatican.va)