They do not care either way
I dropped off my kids and friends for Jonas Bros and they range in age from 9 to 17 and no problem but cant speak for every show.
I think it all depends on the events and their age restrictions. I would check the show info and go from there besides that i think it should be fine if accompanied by a adult or someone of age that you can trust.
As long as they have a ticket. I see them come in and out
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