I know lots of 6 yo kids and only a couple are like this. Same with the 8yo but I don't know as many of them. I wouldn't say it was the norm, but I also don't think it is uncommon if that makes sense. Especially if they are feeding off each other and revving each other up, it can escalate the behaviour.

I don't have any idea how to deal with it sorry! I refuse to look after he kids I know who are like this as they scare me lol.