I can't speak to the adoption and racial difference, but I can tell you that DS5 and a friend's DD4 both do this kind of goofy/bratty behavior and it does seem to be a plea to fit in or a distraction from frustration for both of them.
I have had ongoing issues with DS and piano lessons, with essentially the same type of behavior. VERY frustrating and I don't really have any answers either. But, thought you might like to know it seems to be fairly age-appropriate, or at least age-appropriate for these kiddos who are making sense of their worlds and where they fit in.
Good luck.
