Somebody recently asked a question about doing a Bible study on drugs. I found a few great resources to share.
Focus on the Family has something good from a Biblical perspective. It can basically be a whole Bible study or more if you really discuss the issues. Never assume your youth don't or have never used drugs just because they go to church, and don't forget to ask the hard questions. It shows you are interested and care about them.
Another great resource is Drug Free World. There is a lot of detailed info about specific drugs and how they affect the body. There's a booklet/slideshow and short documentaries by real people. Anybody who leads a Bible study on drugs should use the information on this site to be sure they know what they're talking about.
It's not, "Just say NO!"
GIVE KIDS THE FACTS ABOUT DRUG USE!