Adler uses the word Catholicism, but I’m substituting the word Christianity because I believe the principle applies regardless and because he used that word partly, at least, because he was speaking to Catholics. But this needs to be thought about:
The truth of [Chrsitianity] in religion and philosophy, for example, is no warrant for the efficacy or intrinsic excellence of the way religion and philosophy are taught in [Christian] schools. Only the liberal arts can provide the standard for judging excellence in teaching, for measuring the efficiency of educational means, or for inventing others; and the liberal arts are neither pagan nor Christian, but human.
From Reforming Education, chapter 13 The Order of Learning (1941)
What do you think? Is he overstating? Simplifying? Right on? Then so what?