reasons to stop smoking

How can I get my friends to stop smoking marijuana?
Im in high school and my friends at school also friends with the pot heads (stereotyping I know that smoking marijuana) and since they started hanging out with them always talk about smokin weed and when they want. Me and the rest of my friends tried to convince to stop and they do not believe that there is good reason to stop. I'll still be friends with them, but I hate drugs. Please help! I want my friends back to the way they were when not taking drugs and have been tense.
Stress, that something like a weed now do something like crack or ice or scripts, and worry … Weed is not a bad thing if done every day so I need 24/7…sounds Blaze everyone smoked at one time or another and that you only live once take DONT both back … if they do thats kool if thats kool with no reason to lose a friend .. burn a bridge. I have friends who smoke and others, including non-judgmental and messaging snapshot of it if my IT friends are 24 / 7, but with more a social thing with em dude, but I do not know what to do I think that you could be more open to them, because they may need a friend
STOP SMOKING