Where I live the kids are drilled in school about drug use. When I told my 13 and soon to be 15 year olds about my AH's meth addiction, they had stuff to educate me! They had already lived through the consequences but we just keep talking about it. The most important thing I think is to emphasized that your child has no fault in the addict's using. As far as my kids are concerned, my AH has a severe illness due to trying the drugs, that is now difficult to treat but I'm honest that he also chooses not to treat it. That mostly he's so compelled to use it, that he just can't make good decisions anymore so he can't be around us. Honestly I think whatever is the truth in your situation if fine.