I've been asked by a lot of people lately if their young teenagers should be lifting weights or not. I always return the question "Sure, why not?" and the inevitable answer is something about stunting a kids growth.
Frankly, if you are worried about how your kid is growing, there are other things to consider. It never crosses a parents mind that they allow their young teen to go out and play football and hit and be hit; go play basketball, jump as high as they can, and land poorly; or play baseball and try to throw a 5 ounce ball as hard as they can, over and over and over. These are the things that are going to mess with a kids body; not a properly executed strength and conditioning program.
So, yes, please take your young athlete to see a QUALIFIED strength and conditioning coach. No, just having a CSCS does not make someone qualified to be your child's coach. Observe the attitude around the gym, observe the way this coach handles his athletes and try and see if exercises look like they are being supervised or are the athletes going all Lord of the Flies in the weight room?
A safe, supervised well thought out strength program is suitable for any kid old enough to be able to concentrate on something like that. It's never too early to start to ingrain proper movement patterns for squatting, hinging (deadlifts), pushing, sprinting and jumping/landing. There is a right way and a wrong way to do everything; and the right way is always the safest way. Even unloaded, or very lightly loaded olympic lifts are a great way to get your kids involved in strength training at an early age. It seems to work in other countries.
If you introduce your kids at an early age with the right coach, they should have lots of fun and success with their training. Success here is paramount. I believe that learning how to weight train at a young age will give kids a feeling of accomplishment that you are hard-pressed to find in other areas of your life. If you set your goal at squatting 135x5, the first time you hit it you feel like a fucking beast. Like you could carry the weight of the world on your back. The best thing about hitting a goal in weight training? There is another one right in front of your face. There is no getting away from it. Weights keep you honest; the iron doesn't lie. You might be able to squeak by in history without studying, and you might be able to swing basketball practice on raw talent...but if you aren't in the weight room as often as you should be, everyone in there is going to know it when you don't hit your next goal. The confidence and self-efficacy this will build in your child will be worth its weight in gold later on in life.
Now, go keep yourself honest. Lift something heavy!