supernaturalism is a default human cognitive mode, it is not learned. Living among "New Age" types who are not religious (by their own assertion) but "spiritual," and often raised by parents who allowed them to "seek their own Truth," I have seen firsthand how ad hoc supernaturalistic worldviews can be generated from whole cloth within a generation without any strong outside suasion.
In other words, if one prevented a child from being indoctrinated in Catholic teaching, or forced to recite the Koran, that does not imply they would become scientific materialists. Rather, they would probably generate their own supernaturalism de novo within their own peer groups. Of course not all supernaturalisms are created equal, so the key issue is not indoctrination in religion per se, but what religion. Dawkins', and my own, main problem is the aggressiveness of particular forms of monotheism, to the point of being a clear & present danger to the lives of unbelievers.link