I was half joking but why not treat adults as adults? Restrict access to youth as much as reasonably possible but one fact can't be denied -- weed is much less dangerous than legal alcohol.
But I do think there is some value in honest education programs that really give the facts, because some people incorrectly think there are no dangers to weed and the other side is unhinged reefer madness. Not just say no, more like just think about it, and if you do it, try for some middle path moderation.