I sort of think by the teenage years - you should already have taught kids right from wrong behavior.

And definitely - teenagers are notorious for poor decision making... But for those of us that have admitted to being naughty or a bit wild as a teenager... how many of us would say that parental intervention would have changed things or would just just shifted it to a different venue? Or how many had parental intervention which ended up "straightening them out"? If your parents caught you having sex and yelled at you for it... did you become celibate for the rest of high school?