Watch what you model. The overwhelming majority of illegal drugs are consumed by adults. They're not junkies. They're what the Justice Department calls casual users. They make use of cocaine like some have a beer.
Kids know what their parents are doing.
They go through stuff the same way a parent might. They know what marijuana smells like or what cocaine looks like. And if Mom or Dad uses, and the child loves Mom or Dad, they think it's normal. If someone else steps in and says it's bad, they think that means Mom or Dad is bad. Be firm with others.