What if its not so much about social pressure, but more about social culture nowadays? Let me explain: in some indian american tribes, smoking was the social norm, so nobody had to really pressure into it. All your friends did it, your aunt did it, even your father did it. Today, there are some unspoken rules about soft drugs, and that is that most ppl are doing them at least once every few months... and talking about MJ, most youngs are doing it daily. If soft drugs are your cities´social culture, your sons/daughters WILL be trying them no matter how correct their manners and education are, but they don´t have to throw their life to the toilet. There is a big difference between an explorer and an addict. The addict doesn´t have goals/aspirations in life and feels angry/depressed, and that is why he stays into the bottomless pit of complacency, while the explorer just tries new things, but when he/she becomes conscious that drugs are impairing his/her health or lifestyle, gets the fuck out of them.
I believe the lack of conscience/perspective is more of a problem than giving in to peer pressure.
(Also, hard drugs are another matter entirely, as there is a much steeper slippery slope, but I believe talks about the real damage they can do to your health and life work so much better than talking about not giving in to the offering. Some ppl would accept anything if it comes from a friend without giving it much thought, and that is more about blind confidence than peer pressure.)