While we haven't dealt with it personally, we have friends whose daughter is our son's age. A few years ago when they were in high school our friends had her brought home by the police when they caught her and several other girls smoking pot. She was not charged or anything else.
Of course, a month or so later, while parents were out of town, they got a phone call from jail. The cops weren't lenient a second time.
So even today, at least in some towns, they're still pretty lenient about pot.
The college town closest to us (bigger than ours) doesn't even arrest for under a certain weight. They just give tickets and call it an ordinance violation. They keep it in city court and don't send it to state if the kids show up and do what they're supposed to.