Along these lines, I just noticed this a couple days ago from the Black Cat website/  Kinda cool, and makes sense that, like a rated R movie, the parents need to buy the ticket to show tacit approval and knowledge that the kids are going to this show.  I'm sure it's a HUGE pain, though...(me thinking as a 16 year old trying to get my dad to drive me to a club -- oy):
 
 Black Cat shows are all ages -- 18+ is fine as long as the person does not drink. If the person is under 18 they must have parental permission, and we like them to be accompanied by an adult.