I'm sure it varies from state to state, but there are quite a few clubs here that do 16+ shows and still sell alcohol. I was dubious when my then 16y/o son wanted to see a few of his favorite bands at a local club that was advertised as a 16+ show. So I came along. He went off with his friends, and I went up and grabbed a seat in the balcony. I have to say the club did a great job of checking all ID's and giving wristbands to the adults. They were very proactive making sure no adults bought drinks and handed them to minors as well as making sure the kids were physically safe considering this was a metal show with lots of pits going on. I was impressed, and let him go on his own after that.
The guy who shot this vid was apparently right next to me. My son was on the far side of the floor by the stairs and guitar racks. There must have been 40 bouncers in the crowd, and if things got out of hand I saw them swarm the aggressor and move him straight out of the club. Yes, I survived without earplugs.
One of his friends shot this vid from the floor. I think it's pretty cool that kids are able to see shows of this caliber at their age in a cool setting. Not my style at all, but the kids dig it.