For children's classes in sparring comps I'd like to see the age divisions also split into height/weight type sections after the age of 11. Up to 11 children are roughly similar, boys and girls. After, it can look quite bad seeing the disparities that can happenCouple of random thoughts. First, I don't see a specific problem with some adult interaction with kids. But trusting your instincts and protecting kids from predators is just good sense.
Unrelated (but relevant to the thread) there was a thread a long time ago where a kid was, I think, 15 and competing in a BJJ adult white belt division. He was grappling with another kid. technically an adult of something like 18. Anyway, there was an accident and he ended up breaking his neck. A lot of controversy at the time about whether or not he should have been competing as an adult. Point then and now is that we have age divisions for a reason, and as a general rule, those reasons make sense for most people. But exceptions occur, and I think that's a good thing, not a bad one.