My son has been in an intensive outpatient substance abuse program since the beginning of summer, and has been clean ever since willingly entering the program. We still have this school year and next summer to help him stay on track before letting him move away to college, which is his goal and ours!
So this is not an issue of him trying to evade detection now or later, in college. He is actively working on addressing the issues that led to his overuse of marijuana, as well as doing things to help him adjust, such as finding a new group of friends for this school year (not easy to do), and involving himself with old activities (theater and a cappella group) and new activities (ultimate frisbee, anchoring the school newscast). So I have high hopes (pun NOT intended) that he will stay on this path and not repeat his mistakes in college, or ever.