1. For kids who did whole grade(s) acceleration, how do you shielding them from getting exposed to "mature" cultural information too early?
I have a 6 year-old completing 6th grade and what we do is ensure that @ home, he is allowed to be his age and we limit the "older" content accessible to him (No Nickelodeon, Disney, Power Rangers, etc ..)
Secondly, talk and talk with them, depending on the gap in ages (for our boy 4+ years from his academic peers) a lot of what is said goes over his head and the few things he does get , we talk about at home. When you do talk, talk to them as if they were that age, they can smell condescension and patronizing attitudes very quickly.
By talking to them at a level they perceive themselves at, the message you want to project will be received more positively
