How to help my pothead friend?

ok I have this friend named jaylin that I have know since I was in the 6th grade and I am now in the 9th grade
we were both in honors classes because we had high G.P.A.'s
but during the beginning of the 9th grade jaylin started smoking weed with this dude named nick
I told jaylin that he was smart enough to know that it's bad to smoke pot
and that he should stop
but he won't listen to me
and now he acts differently than he used because he started smoking weed
he used to be a smart outgoing dude who was always very hyper and fun to be around
but now his grades are dropping
and all he every wants to do is go to sleep

what should I do

you should tell his guidance counselor and they can talk to the right people to get him help. if this doesnt work you will have to talk to his parents, let them know that you want to be anonymous and that you are just concerned for his health and for his future. A lot of kids smoke weed in high school to fit and and to rebel against their parents or the world in general. I know during the teen years life is crazy and sometimes hard to understand, but it does get better.

Consider:

Risk-taking behavior and injury are especially common during adolescence and young adulthood. Drug use contributes to injuries among adolescents and young adults because it has negative effects on perception, judgment, and reaction time. A young person under the influence of drugs also has less respect for the welfare of self and others.

You're being a great friend - get him help - just like that commercial where the boy is going down the stairs and says 'you know, my big brother never got in any trouble - never did anything', but that's the problem 'he never did ANYTHING !' - he goes down to the basement and tosses his brother's wallet on the couch by his brother, room filled with smoke - and says 'here's your wallet' - there's a long delay and his brother finally says 'huh ??' (reaction time, judgement, perception, caring)