You might want to do some looking into the "invention of childhood"; what we understand as "children, teenagers, young adults, adults" is a fairly modern way to look at "stages of development". In the distant past, children participated far more comfortably and fluently in adult society than they do today, when they're sequestered away.

It is very difficult to see any representations of this in the US, where most children are in school, so I'll point to examples in fiction: fictional novels or movies where the protagonist is taken confidently through an unfamiliar city by a child who seems to know every location, has a sleeping place, weapons, a method of finding money, and a network of friends. In these works of fiction, the child is almost always a semi-homeless "urchin"; but this is mostly because modern writers can't conceive of a child that capable without also assuming that the child's parents must not be involved in their life, because modern people equate "parenting and raising children" with "making sure children only ever do child-appropriate things".

My question to you: what do you think it would look like if two loving, attentive parents tried to raise a kid with the confidence and skills of those fictional street children, but also actually fed them and gave them a place to live?

It is very likely that the answer to that question is far closer to the way that children used to behave and live than the way that children are today.

I also recommend looking at old tests and study material (pre-1900, ideally pre-1800) for young children. Children can read, figure, write, and remember at a level far superior than they're assumed to be able to today, and that goes for adult socialization as well.