Hmm, this is a topic I have often discussed with my dh. I am a certified athletic trainer; I have worked at high schools for 8 years or so, and wrestling was always...well, interesting.
While I think it may be tough for your son to compete against kids his age/weight class that have been wrestling for a long time, a lot depends on how athletic he is, and how fast he picks up new skills. It is a very intense sport, however, and there is in my opinion a lot of pressure put on the athletes, because it is an individual sport for the most part.
I guess my best advice from my experience is to learn about the sport yourself as much as possible- wrestling coaches are stereotypically very intense people. (Obviously not in every case, but I have run across a few that have been rather excessive on the kids- but this can happen in any sport.) Learn about cutting weight, and how to do it properly- this is THE MOST important thing in my opinion!! Coaches do NOT always help the athletes lose weight properly, and it is to the detriment of the kids, especially those in prime growing ages, like middle school.
Check with your school's athletic trainer, and see what the rules are in your state regarding cutting weight. Here in PA, it became mandatory for us athletic trainers to measure body fat and to do urine tests on all of our wrestlers at the beginning of the year to certify them in a weight class. There is then a formula, which gets monitored and tracked by the state for each individual athlete- they are only allowed a certain percentage of loss per week through the season. This is meant to prevent "yo-yo-ing" different weight classes, but there are definitely ways to "work the system", and there are some coaches out there that will push the athletes to try.
I don't mean to give wrestling a bad name, and you have any other questions, please feel free to pm me about them. Sorry for writing a book, I tend to be very opinionated on this subject, haha. Again, I just urge you to be informed, and know what warning signs to look for, and if the interest is there for your son, let him give it a try.
Best of luck to you!
Lisa