You might try having a chat with the coach and tell him the kid is training for competetion and that any addition weight training may hinder that ... if the coach is not a total ego maniac... I would hope he would adjust the kid's training. If he is an ego maniac and a horse's rump.... squash him ha ha Or just embarass him with facts and data versus his bro science coaching.... or squash him!!
When a person reaches beyond the limits of their ability; they shall they make progress. There is no other way.