kids need to see faces as part of their development, not sure how any of your post addresses that. in the countries you mention it is still not expected for young children to be wearing face coverings while among their peers.
Historically, plenty of societies had kids who didn't spend much time around their peers, aside from family. It's not uncommon for a family to be ma, pa, and kids living on a farm, or hunting-gathering in a forest. The invention of same-age peer groups in schools is pretty modern, on evolutionary timescales.
... and kids see plenty of faces at home and in other non-school settings.