I have been on several sailings where kids acted badly. On one Carnival with a lot of kids who had the run of the ship they heckled an entertainer who was singing in a style not to their taste. Usually the acting badly is on summer sailings with a lot of kids. Had them running down the hall knocking on doors, also pulling off the room service requests. My pet peeve is the hot tub. Little kids will take them over and I have been in a hot tub with no kids and ten minutes later five littles jump in and splash around. They certainly are in bars, the parents bring them and on one NCL cruise a toddler was wailing so much we moved on. On another NCL sailing a toddler was running around in a specialty restaurant. I have been on over 60 cruises so I have seen everything. Yes, even in the comedy club and the comedian warned them he was going to be doing adult humor and they stayed anyway then they stormed out. That said the only thing I do to avoid children on cruises is to avoid holiday sailings. I don't expect a mass market line like Carnival or Royal Caribbean to be child free and I don't mind the children when they are not in numbers that overwhelm the ship.