Editor's note: China Daily was among a small number of media organizations recently invited to take a tour behind the walls of Beijing Juvenile Correction Center.

Li Ming refused to talk about his past, other than to say what he was convicted of and the length of his sentence. "Robbery, in March 2008," he said. "I was given nine and a half years."

The 22-year-old, a tall, thin man with rimless glasses, was sitting across from reporters in a hall at Beijing Juvenile Correction Center.

Convicts play basketball at a juvenile correction center in Beijing on Sept 25. Wang Jing / China Daily

Like every other inmate, Li was dressed in a gray uniform with a yellow stripe across the chest, his hair closely cropped. He rubbed his hands nervously as he spoke.

On arrival at the center, in Beijing's southern Daxing district, correctional officer Chen Donghai said all inmates are unofficially color-coded depending on the risk they pose to themselves or others.

Li was classified "red" when he was transferred to the facility due to his aggressive and disobedient attitude.

"He resisted everything," Chen said. "He argued and fought with other inmates; he even injured himself to get to us."

However, Li's behavior began to change once his family became more involved. "My way of thinking changed," Li said in a quiet voice, explaining how Chen had visited his older sisters and urged them to make contact. Now they regularly write letters and visit, to encourage him to look to the future.

"I was touched by Chen's actions," he said. "I realized that the officers were different from what I had thought. They're not cold-blooded. They do care."

Opened in 1955, the detention center is a large complex surrounded by stretches of grass and playgrounds and houses 12,000 offenders.

Roughly 70 percent of inmates committed violent crimes, such as rape, murder or arson, according to Zhu Guanghua, the center's spokesman.

Each province, municipality and autonomous region has just one juvenile correction center, with the only exception being the Xinjiang Uygur autonomous region in Northwest China, which has three.

Several government agencies and experts were unable to provide data on how many juveniles are detained nationwide.

Although the Beijing facility has about 200, the rest of the inmates are young men who committed crimes as juveniles and consequently came of age behind bars, or adults convicted of misdemeanors that carry prison terms.

The rate of re-offending among young offenders in China was also unavailable.