Went through it 20 years ago and about to go through it in 5 years time.
If you're child gets to 13 and you have not instilled in him/her the virtue of moderation and responsibility then it's too late late to start.
What ever you say they will smoke, drink, date losers, have sex and be a teenager. The trick is to teach them the dangers of going too far and doing these things safely.
I was a hippy drop out in the 60s and learned the lessons of moderation and responsibility before I got to 13 from my parents. Seems not to have done me any harm.