I'm all for adults smoking weed recreationally, but teens smoke weed and get lazy and their grades drop. I'm sure it's also not all teens, I smoked and still did great in school, but if this parent is testing their kid there's probably a problem. The best thing to do OP is to teach your kid to use it responsibly. Or to act like it's totally cool, and see if he just gives up on it. There's really no great parenting answer to getting your kid to stop doing drugs.