For teenagers in many poor areas on the mainland, dropping out of school to take up work in the city remains a tempting option, researchers say.
Why continue to trudge through mountainous areas for hours a day to get to classes, when there is money to make in exciting, fast-paced cities? And for their parents, a high-paying job with a university degree can be a difficult future to imagine.
The central government does not make public statistics on the scale of child labour on the mainland. According to Dr Liu Kaiming, director of the Institute of Contemporary Observation, a civil-society group in Shenzhen, the child labour situation has improved in the past decade, but young people in rural areas continued to drop out of school and take up jobs in cities.
In central and western provinces, the drop-out rate among junior middle school pupils can be as high as 10 per cent, Xinhua has reported.
"Pupils will pay illegal agents to get fake identity cards when they hunt for jobs," Liu said.
Under mainland law, businesses are not allowed to hire workers younger than 16 and offending companies face punishments ranging from fines to loss of their business licences.
Under a previous campaign, small village schools were closed in favour of a single large one located in the centre of a town, forcing some pupils to walk hours to make the journey every day.
Some parents place little value on higher education due to the poor job prospects for university graduates, said Liu Rui, a researcher at the China Village Governance Research Centre of Wuhan's Huazhong University of Science and Technology.
"These children's parents aren't aware that child labour is illegal. They just follow custom and send their children out of their backwater villages," Liu said. "Normally an adult familiar with families in the village will take the kids to cities and introduce them to factories."
One 16-year-old girl from the Yi ethnic minority was sent back to her village in Sichuan province after labour inspectors found her and several other underage workers in a factory in Dongguan , Guangdong, the Peninsula Metropolis Daily reports. She said she previously worked at a factory in Shenzhen.
They had to work for more than 12 hours a day and were not allowed to talk or check text messages on their mobile phone during working hours. They were paid 12 yuan (HK$15) an hour, of which 3 yuan was commission for the agent who set up the job.
Cheng Yanyuan, a labour law professor from Renmin University of China, told the South China Morning Post that a growing percentage of child labourers were pupils from technical schools who attended "work-and-study" schemes at companies during school vacations.
"In some cases teachers don't know the red line is age 16 and there is almost no supervision of this group of pupils," Cheng said.