And the ATF does a nice job at it (barring the exceptions like waco tx and ruby ridge and others). Don't you think the ATF can handle this?

-There are more alcohol addicts per capita post-1933 than prohibition-era.
-Alcoholism has had a massive burden on health care, organ donation eligibility.  Drugs do the same.
-Alcohol consumption has resulted in more accidents and has been a precurser to more violent and/or sexual crimes than there was during the prohibition.
-Alcohol has almost no effect on blood donation as it is easily purged from the bloodstream, but drugs remain present longer and have a more pronounced effect on organs that affect the properties on one's blood.
-Racketeering and smuggling was rampant in that time, though I owe that more to deficiencies in the investigative techniques and technologies of those times.  
-Average lifespan has since increased since 1933; largely due to antibiotics and vaccines--neither of which are effective against organ damage drugs are responsible for.  A greater accessibility to drugs results in increased use which results in adverse health effects.  This has occurred with alcohol post-1933. So it shouldn't be different with drugs.
-When criminal organizations are denied sources of revenue, they invariably try to find it through alternative means, starting with an increased effort in their other activities.  This happens everywhere.  If drugs are part of their revenue, they will behave accordingly. 
-Fetal Alcohol Syndrome has since increased since 1933. This condition impairs one to moderate anger--such persons are far more likely to go to prison for violent or sexual crimes.  Similar conditions emerge when drugs are taken during pregnancy.
-The end of the prohibition era had the US aligning itself legally nearly equally to its neighboring countries.  If the US ended drug prohibition but Canada does not, the Canadian government will tighten its borders, and this means that the US will do the same.
-Dry counties still exist in the US.  When persons from said counties go to areas without prohibition, their alcohol intake increases on average.  Greater accessibility and less legal ramifications results in increased use.  This is reflected in insurance policies.  DUI offenses increase insurance rates across the board; with more people doing drugs, even the perceived increase of risk in certain age groups will result in higher insurance premiums.
-Those most likely to indulge in the increased availabity of drugs are those in their teens and twenties; since drugs have a measurably adverse effect on one's mental function (memory and problem solving in particular), average grades will predictably decrease and the average national IQ will reflect this.

In short, a lot of this happened after prohibition-era 1933, so there is little reason why it will be different.

Speaking from experience, I started selling weed, making a $1000, a week at 15. I can tell you the only reason it was being exposed to kids in school is because suppliers need to off load their products somewhere. Where better than a prison school. Suppliers just want a place to sell.

I'm not sure I understand your point. Kids have always tried to score booze. Why wouldn't they still try to score drugs?

1. It would be more difficult for the youngins to get drugs if it were regulated. Right now, its easier for a young person to buy street drugs than alcohol or cigarettes.

2. The black market would be much smaller if it could only rely on the underage.

That is a really good response. I may not get back to you on that right away, but I will after some fact checking.

Smaller, maybe, but certainly not non-existent. I don't think it would only rely on the underaged. Cigarette smuggling is a big racket because of how high taxes are in certain locales.

It really depends on how onerous the regulations are and how high the taxes. If legal distribution is relegated to dispensaries, then I definitely don't think much would change.

Well, kids don't try to score beer & cigarettes at school. But right now they go there to buy meth.

BTW you make a very good point about over regulation and over taxation. I never thought about that before.

That is true. While i could probably have some heroin on hand in 24 hours if I asked some shadier acquaintances of friends of mine, i wouldn't know where to begin to ask for white lightning around here.

The black market would be significantly smaller and that would reduce crime. Less crime and government spendling less money to regulate what people put in their own bodies are my only concerns.

High taxes would make the black market thrive and therefore they should be kept affordable. Hence, higher taxes just leads to higher crime.