Headup. The difference is when it's done purely as a way to gain a competitive athletic advantage as a repeat 8th grader. When you hold a kid out of kindergarten at 6, it's much less likely you have a specific focus or target to gain a advantage in.

Also when you are 6 and held back, you are not moving to New Mexico for a year and training with the Adamson's. They were a very high profile wrestling family that trained Boaz and Tyler daily at a very high level for a solid year. Don't get me wrong, I like both those kids, but to say that was not a advantage is not thinking it through.