Many of these anxious parents, had no idea how to change their rebellious children.

In 1999, a middle-aged woman visited Zhang with her son, crying for help.

"She told me she divorced her husband when her son was young and sent him to her parents' home in the countryside," Zhang said. "When she brought him back for junior high school in Daqing, she found her son had become scrappy and often ran away from home with some street gangs."

Zhang spent two hours talking with the young boy.

"At first, he seemed quite resistant and refused to talk with me," she said. "I just told him my stories and experience without preaching a sermon to him. Gradually, his features softened and he began to communicate with me."

"When he left, he promised to try to change and pay more attention to his studies, but I knew it would not be so easy," she said. "A month later, I sent him a present – a handmade sweater."