He still had a hefty student loan to pay off and volunteering wasn't helping his own financial condition, but Yang believed these couldn't be reasons to turn a blind eye to the struggles of underprivileged children. "My conscience did not allow me to turn my back on children who needed support," he says.

After volunteering for a year, Yang knew firsthand the problems plaguing local villages, which included acute shortage of teaching resources for rural children, and he was desperate to find a better way to help.

In 2007, he landed a teaching job at Hongyan Middle School in Longshan county, through open recruitment. On his first day at work, he wrote in his notebook that he would never let a child drop out of school. "I did not want my students to face the tough choice my sister had to face," he says.

A few months into the job, Yang received a letter from a student, 13-year-old Zhang Xiaoli, saying that she was leaving school because her parents, who suffer from disabilities, had run out of money even for medical aid.

"I could feel her helplessness as I read the letter. She was eager to continue school, but could not let her parents suffer anymore. I couldn't help but think of my sister — how distressed she must have been," he says.

Yang decided to pay Xiaoli's family a visit, hoping against hope that he might be able to convince them to somehow send her back to school. When he stepped into their one-room house, he was shocked into silence.

The room, barely 20 square meters in area, was dark and dank. The only bright source of light was a fire burning in a pit over which a soot-streaked pot hung. "Two rickety beds counted as furniture and the ceiling was so low that one would hit one's head if one stood bolt upright," he recalls.

Yang learned that the family had been neck-deep in debt for years and there was no way her parents could afford Xiaoli's tuition fee any longer. He was so deeply disturbed that he posted about his visit, along with pictures, on social media.

The response to Yang's post was overwhelming. His former classmates and friends came forward to help send Xiaoli back to school. With funds pouring in from acquaintances and strangers, she finished primary school and went on to study in middle school.