Children in Long Term Solitary Confinement.

"Why lock somebody up while you're locked up? You're trying to kill their spirit even more," says Michael Kemp, describing his six-month stay in solitary confinement at age 17.

Solitary confinement was once a punishment reserved for the most-hardened, incorrigible criminals. Today, it is standard practice for tens of thousands of juveniles in prisons and jails across America. Far from being limited to the most violent offenders, solitary confinement is now used against perpetrators of minor crimes and children who are forced to await their trials in total isolation. Often, these stays are prolonged, lasting months or even years at a time.

Widely condemned as cruel and unusual punishment, long-term isolation for juveniles continues because it's effectively hidden from the public. Research efforts by the American Civil Liberties Union and the Texas Criminal Justice Coalition have struggled to uncover even the most basic facts about how the United States punishes its most vulnerable inmates.

How can a practice be both widespread and hidden? State and federal governments have two effective ways to prevent the public from knowing how deep the problem goes.

The first has to do with the way prisons operate. Sealed off from most public scrutiny, and steeped in an insular culture of unaccountability, prisons are, by their very nature, excellent places to keep secrets. Even more concealed are the solitary-confinement cells, described by inmates as "prisons within prisons." With loose record-keeping and different standards used by different states, it's almost impossible to gather reliable nation-wide statistics.

The second method is to give the old, horrific punishment a new, unobjectionable name. Make the torture sound friendly, with fewer syllables and pleasant language. This way, even when abuse is discovered, it appears well-intentioned and humane.

So American prisons rarely punish children with prolonged solitary confinement. Instead, they administer seclusion and protective custody. Prison authorities don't have to admit that "administrative segregation" is used to discipline children. Just the opposite, actually. It's all being done "for their own protection."

Seclusion? Protecting children? Who could argue with that?

For starters, there is Juan Mendez, the United Nations special rapporteur on torture. Americans are accustomed to the U.N. investigating incidents of prisoner abuse in other countries -- which Mendez has done in faraway places like Kyrgyzstan and Tajikistan. But increasingly, his inquiries are focused on American prisons.

Mendez spoke publicly about Bradley Manning's deplorable treatment in solitary confinement. Now he is calling on the United States to ban isolation for minors, which he considers, "cruel, unusual, and degrading punishment." It's a recommendation he shares with the American Academy of Child and Adolescent Psychology.

The ACLU report, Growing Up Locked Down, is one of the few detailed, comprehensive examinations available. This devastating and detailed look at solitary confinement for minors has led to this online petition that will be presented to Attorney General Eric Holder in October 2013.

Because the prison system is so opaque, reform has been slow in coming. A congressional hearing on solitary confinement, chaired by Sen. Dick Durbin (D-Ill.) last year, heard testimony from mental health experts, questioned the director of federal prisons, and brought a replica of a solitary confinement cell onto the Senate floor. In recent years, seven states -- Maine, Connecticut, West Virginia, Mississippi, Oklahoma, Arizona, and Alaska -- have enacted laws to restrict the use of punitive isolation on young people. As awareness of the magnitude of the problem grows, more reforms are likely to follow.

If we believe that juveniles are inherently less responsible for their actions than adults - and more susceptible to rehabilitation - then it follows that their punishments should be less severe.

Given the severity of the punishment, prohibiting solitary confinement for young people is a first step. The greatest challenge remains demanding greater transparency from a prison system that wields total control over its most vulnerable inmates.