Matdawg makes a good point regarding looking at body fat and all. You have to be careful on this and make sure you have a great scale and body fat measurement tool that is appropriate for age, they do vary from age to age. We finally made that investment (not cheap) but it was worth it. I also agree with Mike Juby that some kids can afford to loose a few pounds.
I would caution that the concept of "cutting" weight for a child this age has to be approached very carefully. If it makes the sport less fun and the kid is in pretty good shape don't do it. If the kid can cut weight by exercise and appropriate diet then I believe that is okay. It has also been my experience that after some time in the practice room that weight will naturally drop if your child is working hard. You would also be amazed at how you can cut weight by eating appropriately, cutting out soft drinks, sugar, etc can make a big difference.
I have scouted various web sites for what I believe are safe approaches to cutting weight. I have posted a page on my web site for wrestling which includes links to information regarding weight cutting. That link is
http://www.furches.org/wrestling/links.html go to this page and scroll down to the bottom of the page.
My son usually cuts 1-3 pounds for a tournament without to much difficulty, it is unique this year in that he is a D5 or 15 or 14 and under wrestler who is having no difficulty making 75 if need be or 78. I must say that he never has to miss a meal for this but I must also say that I often have to make him eat more and appropriately in that he is afraid of not making weight. We remind him of who is in charge on these issues though, and make him eat. I have also found appropriate nurtrition suppliments essential. We have a specific brand that has worked wonders for us (I have already lost almost 40 pounds and anticipate a total of 50 by Jan. 1) this last year year and will be glad to share what has worked in more detail if someone wants to know. I must also say that Nathan has put on an additional 7 pounds of muscle this last year and he is much stronger as a result. Weight cutting can be one of our sports most dangerous and inappropriate habits. Appropriate diet, if done correctly, can be a lesson in nutrition and a healthy lifestyle.