When I was still a kid at SVS, Hanna, a staff member, would often ask me a question I never really knew how to answer. She'd ask, "Jesse, how did you develop such good language skills? You have such a large vocabulary, where did you learn it?" I never knew what to say in response besides, "I dunno, I just picked it up." As an alum studying linguistics and cognitive science in college, I now have a theory to answer Hanna's question.
In one of my linguistics classes at Hampshire we were talking about creoles, languages which develop when children have only a pidgin language to learn from. The classic example is in a plantation society in the Caribbean. The plantation workers have been forcibly removed from their homes and share no common language. The plantation owners speak English (or French).
The plantation owners look down on the workers and only speak to them in "baby-talk." They constrain and simplify their language so much that the underlying syntax isn't even apparent to the workers who don't know the language. It was mentioned that this is the same way "anyone talks to a child" to emphasize the social hierarchy affecting the situation. Language is never taught, only acquired. The workers take vocabulary from what is called the "superstrate" language, and put it over their own language's existing grammar, which is called the "substrate language." The result is called the "pidgin language" and it is severely limited in function. A pidgin language only expresses directives and descriptives. For example, "There's the field" or "Go work on it."
The creole is formed when children are born into this environment and have no language to learn from their parents but the pidgin language. As babies and toddlers, they take this pidgin, changing and evolving it into a full language. Over the course of a few generations, it quickly evolves into a full language that can express anything any other language can express.
So, going back to Hanna's question, if most children grow up in environments where everyone talks to them in simplified, constrained grammar, under the assumption that they aren't smart enough to understand, and only ever gives them directives like "sit down" and descriptives like "this is on the test" then perhaps it would have a similar effect as in the formation of pidgin languages. The children aren't being given enough unconstrained data in order for their brain's Language Acquisition Device (the LAD as described by Noam Chomsky) to properly analyze all the different aspects of their language's syntax. Of course unlike plantation workers, they do still have plenty of access to their language and do learn it, but it's not until they get older that people stop talking to them in constrained simplified ways. You can see how this would impede acquisition of language skills, yes?
In answer to Hanna's question, my theory is that my language skills came from being in an environment where people weren't afraid to talk to me as an equal, despite my being seven years old and their being 45. I was exposed to the full breadth of words and syntax, all the different complex constructions you can make, and acquired them naturally at an earlier age as anyone else would if they had access to them. When older students and staff didn't constrain and simplify their speech around me, it gave me more data from which to acquire language as a child. I didn't have to wait until I hit that magic age where people decided I was going to be smart enough to understand relative clauses, or to use "higher-grade” words..
Maybe our kids would pick up language skills faster if we allowed them natural access to the full language, rather than dumbing things down automatically just because of their age.