I don't understand why drugs have to be scary. The boogieman attitude doesn't work with youth, it may work for a 4 year old, but not a teen especially with the access they have in regards to the internet.
By graduation
nearly half (48%) of youth have tried tobacco, even more at
just under three quarters (70.8%) of all youth have tried alcohol and about
60% of youth have tried marijuana and if you expand that to illicit drugs that number can only increase.
Now I'm going to go way out on a limb and say the percentages are probably even higher because usually when someone is breaking the law (underage drinking, illicit drug use) they aren't going to reveal everything, especially to the government.
Anyways, put it all together and by the time your kid graduates the odds are overwhelming they've tried at least one addictive substance. But if not, don't worry there is lots of time in college and university.

And to be straight honest there is nothing you can do to stop them unless you're going to lock them in a basement and eliminate all social interaction. Most likely a youth will attend a party that has drinking and smoking and they will be offered other drugs.
All you can do is educate them but you can't just make stuff up and scare them off of it. They have tried that in numerous ways and one of the most popular ones was "Just Say No" campaign that flooded schools and airwaves. The problem with the campaign is they blatantly exaggerated and gave false information about the use of all drugs, legal or not. Basically telling children that one marijuana cigarette would destroy your life making you useless to society and alcohol would turn you into a booze riddled wife beater and that one hit of crack you would be addicted for life. Don't get me wrong crack is horrible! However
only 7% of people who try crack become regular users.
So what happens when your child sees the laughable difference between the stoner at school and the one depicted by commercials and their parents? What happens when a child sees someone do the worst of the worst (crack) and over 90% come out unscathed?
The trust is ruined, gone, done. “If mom/dad/teachers/commercials have been lying to me about this, what else are they lying to me about?”
Most youth drink, smoke, and do illicit drugs because of the taboo and "bad ass" nature of it. Do you remember doing something your parents told you not to just to find out it wasn't what they said? Why do people think it will work on their kid when it didn't even work on them? I understand why parent want to protect their kids, I’m the same way with my brothers. They both know I smoke marijuana but they also both know I didn’t start smoking until I was 19 and I would be the first person to spark one up with them when they reach that age as well. At least that way I know for sure what they are smoking.
What parents should do is educate their kids on what drug abuse
really is. And that means letting them know the difference between being a recreational user and how it is a fine line before it turns into a dependency. Is one marijuana hit going to turn you into a low life loser? No. But if you are 24/7 perma-fried it's going to cost you money, relationships and possibly land you in jail, no matter what anyone says any drug is bad, even too much caffeine can kill someone. Will having a few beers with your buddies turn you into a raging wife abuser? No. But drinking irresponsible could make you end up being a parent yourself or in trouble with the law, and drinking and driving is a good way to end up dead. Give them reality, not the boogieman effect.
Now in saying that I think more and more parents are starting to realize this because as education has increased and scare tactics decrease we have seen a drop in all drug use (alcohol, tobacco, marijuana, cocaine, etc.) with the youth in Canada in the last decade. I've noticed a huge shift on how my brothers (14 & 16) are taught about drugs not frightened by them. But I still see/hear a lot of parents give their child false information thinking it is helping them and it isn't, kids aren't stupid. If you tell your child their life will be ruined by one puff of marijuana and then they try it (because they will!) and realize you lied, they may wonder if you lied about crack, cocaine, heroin, meth, etc.
In a perfect world your child will be introduced to drugs in a controlled environment with responsible adults who could provide a safe environment. However, the truth is, your children will probably try it the same way most of us did. In a friends basement while his parents are away, yelling over loud music, blinded by a thick layer of smoke.