Theaetetus: By the gods, Socrates, I am lost in wonder when I think of all these things, and sometimes when I regard them it really makes my head swim.Wonder is often supposed to be the special provenance of children. This supposition is perhaps another aspect of the so-called "invention of childhood," the ostensible cultural shift in the west which (it is claimed) gave us a new construal of the difference between children and adults. The historian usually credited with (or blamed for) the idea that childhood is a modern construct is Philippe Aries, who pointed out, among other things, that before roughly the 1600s, children were visually represented in Europe as miniature adults. Among thinkers, Locke and Rousseau are frequently associated with this re-construal, which cast childhood as a window of innocence and goodness and vulnerability.
Socrates: …. This feeling of wonder shows that you are a philosopher, since wonder is the only beginning of philosophy, and he who said that Iris was the child of Thaumas made a good genealogy.
--Plato, Theaetetus 155d
It is through wonder that men now begin and originally began to philosophize; wondering in the first place at obvious perplexities, and then by gradual progression raising questions about the greater matters too, e.g. about the changes of the moon and of the sun, about the stars and about the origin of the universe. …thus the myth-lover is in a sense a philosopher, since myths are composed of wonders.
--Aristotle, Metaphysics A 982b
I am dubious about such historicist claims that such-and-such a phenomenon was "unknown until..." some date that usually winds up being suspiciously late. (Similar claims are made about homosexuality and romantic love, for instance). Talk like this has a tendency to become overblown and to foment the worst sorts of historicist relativism. We do well to beware of anachronistically projecting a contemporary perspective on the past, but such due caution is not the same as thinking that the "new" development was unprecedented and would have been unrecognizable to previous ages. (Similar arguments are made about "judging history" by contemporary values, and here too, one must walk a careful line. There is such a thing as anachronism, of course, and I take the history of modes of consciousness seriously, especially as informed by technology -- which really does change; in thinking about these things one is continually compensating in one direction and then the other).
There is plenty of evidence to show that children were always seen in certain ways as different from adults – for instance, the fact that they are counted (or sometimes not counted) separately. Example: when the New Testament recounts the miraculous feeding of the multitude, it specifies: "The number of those that ate was about 5,000 men, besides women and children." And one could also point to all the specific emphasis Jesus puts on children, which cannot be explained away as sentimental Victorian haze even though it was surely obscured by such sentimentality. Whatever the real differences between children and adults, it is certainly not unreasonable to suggest that this difference has been read in more than one way from era to era. Why this alleged shift should be described as the "invention" (and not, say, the discovery) of childhood is not obvious; but it's at least arguable that the idea of the child as especially prone to "wonder" is an instance of such ideology at work.
In short, I think that the notion of "wonder" is associated with children for good reason that modernity may have magnified but which it did not invent. And yet, in the same era that would have (per hypothesis) projected this image of the naturally-"wondering" child, specifically engaging the very young in expressly philosophical discussion has more and more fallen out of practice, except in the most informal or "framing" of contexts. Teachers may allow themselves a philosophical aside, or discover that they and their young students are having a surprisingly wide-ranging conversation, but in modern academic pedagogy, philosophical instruction tends to begin in undergraduate years. The notion of intentionally presenting philosophy to young people (between elementary and high school) as an investigation in its own right is (for the most part) foreign to primary education.
What does this say about our presuppositions about pedagogy, about philosophy, and about the "wonder" from which philosophy supposedly springs? Might the modern "disenchanted" world – a world from which wonder has (supposedly) been banished – be a symptom, a cause, or both, of our assumption that philosophy is a matter for "adults"?