I got semi-curious about this issue of the use of drugs and alcohol, and the comparison between private and public schools. I recall one of my high school teachers relating his experience that private schools have more alcohol abuse, but public schools have more drug abuse. But that was 25 years ago, so I doubt it's still applicable. Here's what I found ...
Availability of drugs to teenagers: Even among teens that do not use drugs, it is acknowledged that they are fairly easy to come by. 29% of teens in grades 9 through 12 report that illegal drugs were made available to them on school property. Not only that,
38.4% of teens in public schools report that drugs are readily available (as opposed to 22.4% at private schools). Teens in upper grades report greater access to drugs than do teenagers in lower grades. And 62.9% report that street gangs are present to sell the drugs.
http://www.teenhelp.com/teen-drug-abuse/teen-drug-abuse-statistics.html
Public school teachers are about 3x more likely than private school teachers to report drug and alcohol abuse as a serious problem for their students. Not sure if that means the public school students are using more, or have more problems using, or even maybe whether public school teachers are just more conscious of the issue.
http://nces.ed.gov/programs/digest/d05/tables/dt05_071.asp
The survey suggests there’s been a big jump in drug use in private schools. In 2011, 36% of private school students said their school was “drug-infected.” But in the past year, that figure jumped to 54%. It was the first time in the history of the survey that a majority of private school students reported drugs on campus. The overall proportion of high school students, public and private, who reported drug-infected campuses was 60%.
http://schoolsofthought.blogs.cnn.com/2012/08/22/survey-17-of-high-schoolers-drink-smoke-use-drugs-during-school-day/
For perspective, consider how the gap is closing:
In 2002, 46 percent of students at public high
schools said their school was drug infected
compared to 24 percent of students at private
high schools; in 2012, 61 percent of students at
public high schools said their school was drug
infected compared to 54 percent of students at
private high schools. The 22 percent gap has
narrowed to seven percent.
http://www.casacolumbia.org/upload/2012/20120822teensurvey.pdf
Interesting to see that Nancy Reagan and her "Just Say No" campaign was seemingly pretty successful.
http://www.drugabuse.gov/related-topics/trends-statistics/monitoring-future/monitoring-future-survey-overview-findings-2012
This mostly relates to drugs. I'm bored now, so I'm not searching for alcohol comparisons.