revo... good call
the bodies of adults and adolescents respond entirely different to training stimuli. whereas adults experience morphological adaptations ie. hypertrophy, adolescents typically experience mostly neurological adaptations and experience minimal hypertrophy, although there is some. there is research however that shows resistance training in adolescents and children is extremely beneficial, especially pertaining to muscle strength, performance, decrease in rehabilitation time from injuries, as well as an overall decrease in the likelihood of obtaining a sport injury to begin with.
you're right, this kid will grow eventually, from his growth spurt that will be hitting him in the near future i'd imagine.
it's cool to see young guys like that in the gym busting their ass. makes me wish i would have started a lot earlier.