Don't bring it up until they do. Make sure to wait until it's on THEIR mind, then tell them what's on YOUR mind. They both sound like very cool parents, just afraid that their son is going through something in his life that is forcing him to use drugs to make him feel better.

I don't think they'd make you stop, they both sound pretty cool. Just tell them like Alive and Zeebo said and all, it won't affect your grades, and you won't be doing other drugs as long as they don't make toking out to be the devil, adding more stress to your already stressful life.

I think they'll be cool with it.