How long has he been lifting at that age?
On that note, what is perceived wisdom re when kids can start to weight train? My son is 11.5 and has asked.
A quick drive-by to answer this.
The stunting of growth and hormone interference that people seem to worry about with strength training is not backed up by any mechanistic or epidemiological literature.
HOWEVER
There is a big problem when parents hyper-specialise their children into an extremely limited movement pallet by getting them into powerlifting. Humans need to be exposed to a broad range of movement stimulus to be healthy, and particularly as children we should be playing and experimenting with a wide variety of stimuli.
In general, parents should not worry about about the use of weights in strength training. The body is also a weight, and sprinting and bouldering/climbing are extremely low risk. Exercise selection is important though. It's a complicated topic*, but effectively I'd advise that bilateral barbell movements comprise a relatively small percentage of weekly volume.
*Think of it this way: do you really know the movement prerequisites for a low bar squat? There are good reasons that the top end of S&C doesn't rely on highly constrained movements. Even as a powerlifter, if you aren't including movement variability into your programming you're a ticking time-bomb of movement deficiencies.