Wanna get high?

Cause that's the students here are doing... okay maybe not high, the are at least smoking... I haven't caught them with pot or drugs yet. So its a really big problem here since yeah there is a legal age that one is allowed to smoke, and of course since when did students ever listen to such rules? Well anyways after classes finish in the evening at around 9:30 or so, most or all the teachers go back to their homes. There are hundreds of students still milling about.. from grade 7 to grade 9, and I like to chat with them and hang around them. Well its the time that i've noticed several smoking which I as a 'teacher' should do something about, so I go after then and put it out. But since they dno't see me as a real 'teacher' in the sense that I don't necessarily have punitive powers (nor do I want them) they like to goad me into chasing after them ... I do have fun doing that and no once I catch them I don't beat them down or send them to a higher authority. Though I do get to say things like... "Are you talking to me? You dno't want me to come after you do you?, A storm is coming and you don't want to be there when it does." Though I have started to see a pattern, (i've only done this twice so far) but a group of them call out to me and point to their other friend that 'he's smoking' and they pull out a but and start puffing on it... Glad I don't get any respect from those students - and so the hunt begins.. it doesn't last long. I'm quite fast, after I take out the but I tell them 'using hand motions' that if I catch them again they'll be getting in trouble again. But of course at that age.. gr 7 gr 8, they love to test your limits and i'm just doing this part of the job - fulling the role of the teacher - but next time they try to do it i'm gonna walk away just to throw them off... I'm sure they smoke in their off time but if me chasing after them gives them a rush and encourages them to smoke more in front of me then that doesn't help either.