AMONG the unintended consequences of China's headlong economic growth are 58 million "left-behind" rural children whose parent or parents have moved to cities like Shanghai to find work.

Photos of a little girl sitting in class with a baby in her arms have caused an outpouring of concern over the plight of unattended rural children whose migrant parents are working in faraway cities.

The girl, 9-year-old Long Zhanghuan, was a second-grader when the photo was taken in July at a village school in the mountainous county of Fenghuang in China's central province of Hunan.

Long is now a third-grader attending a different school even further away from home. The baby boy is her cousin. Long took him to school because she worried her grandparents were too busy to keep an eye on him.

Long and her cousin belong to a lonely group that is known in China as left-behind children, or liushou ertong - an estimated 58 million children in the custody of a single parent, grandparents and sometimes a distant relative or a neighbor.

Their parents have migrated to cities in search of work.

China has around 180 million migrant workers, a floating population once as high as 200 million; numbers have fallen as the number of manufacturing jobs has fallen.

The photo collection titled "Hush, Brother Is Asleep" has spread quickly on the web after being posted last week at Sina Weibo, China's most popular Twitter-like microblogging service.

Many Internet users posted comments, saying the maternal, nurturing expression on Long's face and her baby cousin's disproportionately large head - a sign of malnutrition - drove them to tears.

"You cannot help crying when poverty, helplessness and all the tough facts of the left-behind children's lives are epitomized in one snapshot," said an Internet user known as "Yannong."

Of the 34 students at Long's former school, which has only three classes - one each for preschoolers, first graders and second graders - only four are living with parents, says their teacher Wu Xiaohui.

Since their village is very close to the school, their unattended younger siblings often are taken along to class, says Wu.

Photographer Lu Qixing didn't expect his photos would make him famous overnight. Lu, who is 55, joined a team of volunteers teaching at Long's school in mid July. The summer holiday had begun, but all the students were called back to school to attend a four-day interactive course with the volunteers.

Long's grandparents, aged 59 and 54, have three sons and two daughters. All of them are working away from home, leaving behind eight children.

"All the children behave well. The older kids have learned to help their grandmother in the field and around the house," says their grandfather Long Titing, who is disabled and spends most of the day at home.

Long Zhanghuan is the second-oldest child and often helps with farm work, cooking and baby-sitting younger cousins. She also carries water from neighboring villages because their home village in Shanjiang town is extremely arid.

The hard work is not fun but the real pain for these children comes from missing their parents, says teacher Wu.

"When we read a text about springtime in class, one boy said he hates spring," Wu says. "He said his favorite season is winter because his parents often come home in winter (for the Chinese Lunar New Year Festival) and leave again in spring - and this brought silence to the whole class."

Wu calls the plight of left-behind children a "deep wound in Chinese society." Others have used similar imagery to describe one of the unintended consequences of rapid urbanization and modernization, leading to a wide gap between urban and rural areas.

After teaching for 11 years in the remote village, Wu says he is familiar with the left-behind children's suffering. "They appear to be strong and carefree, but I know they are fragile at heart."

After Long became famous on the web because of her picture with her baby cousin, many people have telephoned the school and offered to make donations for her family's welfare.

"These calls came suddenly and caught us unprepared," says Wu Yansheng, principal of the village school. "But Long is not the only left-behind child in our county."

The principal said the school plans to work with local government to set up a fund for all the left-behind children in Fenghuang.

Noted sociologist Wang Kaiyu says the long-term remedy to their plight is to narrow the urban-rural gap and create more jobs in the countryside so parents can make a living and don't have to migrate to cities in search of work.

At the same time, Beijing University professor Lu Jiehua suggests cities grant migrant children equal access to public schools, medical care and other social security services.

In general, only the holders of urban hukou or household registration are eligible for its benefits, including free education and other services for residents.

Around China, benefits are linked to hukou, so when people migrate to cities, they have no hukou. Thus, though parents might want to bring children with them, they face problems of access to education and health care. Many private schools set up for migrants' children are substandard.

Reforms of the hukou system have been proposed and some pilot projects are underway, granting hukou to migrants who meet various residence requirements.

Retired teacher Zhang Bingzhu, 72, has opened a free care center for left-behind children from his home village in Chaohu City in eastern China's Anhui Province, a major source of migrant laborers.

Over the past five years, he has cared for dozens of children, reading them stories, helping them with school work and playing games.

The provincial government of Anhui plans to open at least 1,000 care centers for these children in the next three years; they will have TVs, books, magazines, sports facilities and phones so children can call their parents at any time.

Many rural areas, particularly in Henan, Anhui, Sichuan, Jiangxi, Hunan and Guangdong provinces, seem to be missing a middle generation of adults.

There are old people and very young people. Grandparents work in the fields and care for the children. Parents have migrated to cities.

China's migrant workers fuel the country's fast-growing economy. They toil as construction and factory workers, waiters and waitresses, cooks, domestic workers, drivers and take other unskilled jobs.

Migrant workers left home for cities in part because of their children. They need money for education fees, health costs and other household spending.