At that point, parents need to start giving them tips about how to say 'no' to peer pressure.
A lot of parents think it's a difficult subject, talking to their kids about the dangers of drugs and alcohol. They don't know what to say, when to say it and where to begin. So they end up starting too late.
If you start talking to your kids when they're really young, they're not going to notice anything different. It's not going to be that big awkward moment that parents dread.