Question

Friend started smoking marijuana with some people you know from school he smokes each time you are around the people from school and you have decided to talk with him about it what can you say to address your concern

Answer 1

You could say something along the lines of:
"Hey, Friend, what's so good about weed? Why are you always smoking it?"
If he's smoking it for medical purposes, then just drop it, but if it's illegal and he's doing it to "look cool", then I would further ask questions about it.