Good topic with many good responses. My son started when he was 7 and is still wrestling at 13. He has 2 state championships and has placed in the top 3 in state 7 times. He also has placed in numerous national championships including winning one and I would consider him a great little wrestler. I will give great validity to all of the posts up to this point, with the possible exception of maybe one. There are I believe, a couple of other things to consider however.
1: Location of practice and practice room facilities need to be also taken into consideration. Is the facility, coaching and wrestlers age appropriate for the child. For example, I have seen many smaller children practicing in a room and become a distraction to the other wrestlers in the room. This is certainly the case in drills and conditioning. I have seen many of the little guys and gals literally get ran over and knocked around. Parents should not place their children in a room that is not suited for that kid.
2. I think that children of all ages can benefit from the basics of wrestling. So in some ways I have found that the case is not always if the child is ready, but are the parents ready? As someone who has done quite a bit of study on child behavior it is primarily important that the parents be able to handle the stress and intensity of wrestling. Often times, if not most of the time, the reason for burnout and bad experiences center around the parents more than the children. I know that even for myself this was the case for the first 3 years of my son wrestling. I as do most parents, have melowed out over the years and my son enjoys the sport now much more because of it. That is not to say that at times he doesn't have difficulty, it is a tough and grueling sport when you compete mostly year round and on a national level. It is important though to allow your child the opportunity to have fun and even experience other sports. Once you see where your child excels then maybe push as you need to for that sport but still allow individual freedom. This is one of the things that the movie Reversal is actually quite good about in my opinion. It shows a loving father that goes over the edge and the consequenses of those actions. While some may be critical of the movie I believe from what I have seen and observed that those things happen far to often.