Toi – you will be happy they do nothing worse. But why are you happy they smoke and drink? If you can stop them drinking and smoking, why don’t/won’t you?
As a Bochur, i can tell you that if you ban everything, you will get nowhere. But there was a time where a group of boys were getting drunk on Thursday nights, and the Yeshiva closed the dorms for thursdays every week for a month (Everybody lives within an hour from the Yeshiva), and then reopened it ?? ???? that the bochurim agree not to drink. And it words – out of the whole Yeshiva, only two boys got drunk the whole Winter Zman (5 Months).