In American culture. Or, to be more exact, in united state settler culture, as we don't know for sure how natives viewed thing. A lot of SA native still have three gender to this day ('girls' and 'boys' are considered neutral and use neutral pronoun until puberty) and it is possible that this cultural factoid stems from a very ancient branch.

And since they don't have 'miss kindergarten' weird hypersexualization of little girls that (imho) border on pedophilia, I'd say I prefer kids not to be gendered in my language.