Is drug use 'normal' 'common' 'acceptable' - is zero tolerance by parents unrealistic?

[13months]

And will it backfire - Should I just be getting informed - and make sure DS is and then watching out for problems - like problem drinkers?

no and no

What do you mean by "zero tolerance"? If you mean you'd throw them out if you found weed in their coat pocket or whatever, obviously that could backfire big time. If you mean you will make clear that you do not approve and won't allow the drugs in your house, that's different. Do get informed and think about what you would do if you did find out say that your child was smoking cannabis at the odd party - bear in mind that the clampdown on under-age drinking and smoking and the fact that most pubs won't let teenagers in to nurse half a shanty in the corner all night, means many teenagers have much easier access to illegal over legal drugs.
They may disagree with the law but respect your opinion on it, but if say you treat their friend ending up in A&E after drinking too much very differently to their other friend who does well at school but can provide the odd eighth, they may lose respect for your opinion on risks.

When I was in my late teens about twenty years ago cannabis use was very common amongst some of my friends. I am also sure their parents weren't aware of it (apart from the boy who got expelled when he was caught with cannabis in school). I regularly (at least once a week) smell it when I am walking through town (I work in the city centre), so I think in some quarters it is common.
I would strongly discourage my kids from taking it, due to the link to schizophrenia (which wasn't known twenty years ago) and because it's illegal.
As pp mentioned, alcohol can also be a dangerous drug.

Drug use is not common or acceptable. Period!

Zero tolerance is not realistic!

Whilst drug use is not common, some parents will come across their DC's use and simply saying it will not be tolerated will just serve to drive drug use underground and in secret.
I would rather know what my DC are taking and be able to guide them appropriately on the dangers.
It is illegal, there are adverse side effects and whilst perceived as 'cool' and 'hip' I'd rather my DC's knew what they were getting into.

I think drug use is quite common, not acceptable and zero tolerance is not realistic.

I can't believe you are asking the question!!!
Drug use should not be acceptable, unless you are claiming your space on Jeremy Kyle! I have 3 teenagers and wouldn't tolerate any of them taking drugs of any sort.
Watch out for addictive personality traits, if there is anyone in the family with addictive habits of drink or drugs, then you really need to stop any problem before it gets started, or you are in real trouble.

ourhouse so what would you do if you discovered one of your teenagers had tried drugs?

You say you wouldn't tolerate it- so what would you do?

Zero tolerance is a standard. If you set that as your standard and you discover one of your children has taken or tried drugs, they know it's not acceptable. If you have a standard that says "well it's not good, but it's ok as lots of teenagers do it" then surely that's a green light for any teenager.

If I found out that one of mine had tried drugs I would talk to them and make sure they understood the severity of going any further than trying them. If I found out they used on a regular basis, I would stop allowances and set in place consequences. I am the parent and it's up to me.

I'm not living in the dark ages, and I tried drugs as a teenager, but also knew if my parents found out I would have been in huge trouble!

It's all about the standard you set, the more parents except it as normal, the worst things will get!