China has vowed to reunite families and return dropouts to school after publishing its first comprehensive study on left-behind children.

Following a door-to-door survey that began in March, the Ministry of Civil Affairs has said that 9.02 million children age 16 or under have been left in the countryside by migrant worker parents.

The research found that more than 90 percent of them are growing up without either parent and are in the care of grandparents, friends or relatives. An additional 360,000 have no guardian.

Huang Shuxian, the new minister of civil affairs, who chaired a multi-department meeting on Wednesday, offered three solutions to ease the problem: encouraging parents to return to the family home; giving previously unregistered children hukou, the household registration that gives them access to healthcare, education and social welfare; and getting the 16,000 children who have dropped out of school back into the classroom next semester.

Huang said many parents of left-behind children have changed their mind and realized that spending time with family is just as important as making money.

But he also criticized some local governments for not doing their best to help these children, which has resulted in their lack of proper custody, dropping out of school and suffering from mental problems.

Yang Jiucheng, 42, has been running a service for left-behind children in Shaanxi province's Pingli county since he founded it in 2007. Most parents in that region go to big cities to find work. Paid by parents, Yang offers food and housing to children and makes sure they stay in school during the daytime.

The top-level attention is great news, Yang said, but he wants more.

"These parents can earn several thousand yuan a month in cities, but when they come home, their income drops to 1,000 yuan ($150) or so. How can they feed their children this way?" Yang said. "We need something more concrete, to give them space to do business or get better jobs back home."

Zhang Juan, who leads a public welfare program to help left-behind children in rural kindergartens by providing special training to their teachers, said, "Most of the parents I know had to leave their children, not because they wanted to, but because they had no choice."

Her cousin works in Guangdong province with his wife. They left their three children in a village in the Guangxi Zhuang autonomous region. The mother moved back once, only to find that she could barely pay for her children's medical bills.

Before the official report, Chinese media widely cited an estimation by the All-China Women's Federation that set the number of left-behind children at more than 60 million.

The latest research has narrowed the group to children 16 years or under, with both parents working far away or one absent, the other incapable of caring for them. That in part contributed to the variation in figures, according to Gao Xiaobing, vice-minister of civil affairs.

The other reason is the government's progress in poverty relief and social welfare, Gao said.

In February, the State Council issued a national guideline to governments at all levels on how to better help left-behind children and said that by 2020, the number of left-behind children must be significantly reduced.