No grade skip here. OHGrandma is right - cubs are by age/grade, boy scouts progress in rank independently. DS absolutely LOVES BS, even though there are no other GT boys in the group. The amount of social skills he learns there is astonishing.
Last winter DS was writing SAT/ACT for the talent search while his older friends from BS were writing it for real(Juniors, wanted to take some university courses). Afterwards DS never advertised his score as it was clear that got by far the highest in the group. We also never discussed it, but I did witness some evasive answers on my son's part. I figured it was his call...