It should be age appropriate. I'm an educator, and I get this question a lot. We should discuss substance use when we discuss other issues young people need to learn about, like how to address alcohol and safe sex, and we should not separate it out. Put it in the entire package when we discuss, at an age-appropriate level, of course, with our young people how to keep them safe, and we should focus on, as much as possible, reducing.... Abstinence is always a goal when we talk to young people.
When we take a harm-reduction approach, that also means they stay safe. As we all know, we'll never get all teenagers to abstain from having sex, but we want them to be safe. By the same token, we want teenagers to be safe if they use substances.