Deterrence doesn't work because criminals don't consider consequences
Every study on the subject has proven that specific "deterrence" as a strategy for lowering crime is not only ineffective, but counterproductive. Societies with harsh prison prison systems have both the highest crime rates and the highest recidivism rates.
Here's one persuasive essay on the topic, which mentions the original "Scared Straight" specifically: web.viu.ca/crim/Student/S%20Wu%20Deterrence%20Theory.pdf
Another recent article: http://www.youthtoday.org/view_article.cfm?article_id=4566
Criminals act out of passion, desperation and the influence of drugs and alcohol. In the heat of the moment, they don't think about getting caught, much less going on trial or being punished.
Instead of trying to scare kids about the realities of American prisons, we should be concentrating on prison reform and actually making it an effective system. The "prison-as-hell" model only teaches our youth that life is cheap, people are horrible and the state condones violence, rape, abuse of power, gang warfare, suicide, drug abuse and racism inside. That's how you breed white-collar first offenders into killers.
The most effective prisons in the world are, perhaps surprisingly, the cushiest. This is hard for some people in the western world to accept, who often tend to think criminals of all stripes as "evil" and "hardened." But nations like Norway and Finland, where the jails are relatively pleasant and inmates are treated like human beings, have the lowest crime rates and, most importantly, the lowest reincarceration rates.