re: Any “safe” hormones/peptides/etc…to help teenager maximize height?

I suggest trying a diet w real food and a fitness regiment focusing on strength, hypertrophy, endurance, and cardiovascular training.
W a proper diet and a vast variety of strain on the muscular skeletal system it can kick start a health chain of reaction on the endocrine system.

Also if he is athletic enough to play basketball he is athletic enough to be really good at other sports.