When I was in high school we had a GREAT speaker come and lecture about drugs. I remember his stories, and how he would shout, "FOR WHAAAAAT." It was so powerful. He had private meetings after the program where kids could meet in small groups and discuss, etc. It was probably the best thing I experienced in high school. And I never did drugs! Really have a hugely powerful speaker come in, and then break down into small groups to discuss.