Parents are experts on their own kids, so they should trust their instincts. I've seen it both ways; lots of families do bring kids and can learn a lot by watching their child interacting with camp directors, reacting to photos, slides. But if you have a very young child, it can be really overwhelming for them. It's a total judgment call.

Sometimes children are ready to go before their parents are ready to send them.

Six years old does sound young, but there are so many (overnight) camps with extremely successful histories of creating a child's world for them. It's a judgment call as to when a child is ready. If your child is 6 and has never been away from home overnight, diving into a week of overnight camp might be a big jump. Families should create progressive experiences to get a child ready.