Around 61 million children are left behind in China's rural villages and towns while their parents work in the big cities.

Li Yikui is a 13-year-old boy who radiates warmth and friendliness. But inside he is hurting.

"I love to be with my classmates, so that I don't feel lonely," he said.

Yikui has not seen his father in four years. His mother visits just once a year.

When he is asked if he misses them, a big tear rolls down his cheek and he covers his face with his hands. It is a silent, but eloquent, answer.

Yikui is one of the millions of children left behind, the hidden casualties of China's rapid development.



Studies show about 70 per cent of the 'left-behind' kids suffer from emotional trauma, depression or anxiety.

Sorry, this video has expired At Xiaping school about 40 per cent of students are growing up without parents

They are sometimes called the lost generation, or the damaged generation.

About a third of the left-behind children — 20 million — will get involved in crime, while another third will need time in mental health institutions, according to a small Christian NGO called Children Charity International (CCI).

"I can't imagine what that would do to China," CCI founder Joseph Lim said.

So far young Yikui is staying on the right path.

We meet him in a noisy classroom at Xiaping school in central China's remote and mountainous Hefeng county.

About 40 per cent of his classmates are growing up without parents. They tend to lag behind other kids in their grades and behaviour, so they need extra help.

"The left-behind children lack the care and guidance of their parents. So they lack self-discipline to some extent," vice principal Mr Xu Liang said.

More than 60 million Chinese children are paying the price of their country's dash for prosperity. ( ABC News: Wayne McAllister )

'I'd be a burden'

Most parents of the left-behind kids are willing to sacrifice a family life in hope that the money they make will provide a better future for their children.

That is a bargain that Yikui understands. He knows he has to make sacrifices, just like his parents.

"If they'd stayed just because of me I would feel guilty. I feel I'd be a burden for them," he said.

Yikui spends the week living in a school dormitory but on weekends he makes a two-hour hike up to his family's mountain-top village.

That is where he gets cared for by his grandparents, like many left-behind children. His grandma acknowledges that it is not ideal.

"It would certainly be better if his parents were here with him," she said.

"We're not well educated so all we can do is try to tell him to be good and listen to his teacher. We can't do much more than that."

As we look out over the valley Yikui tells us there are only old people in the village these days. All the parents have left — and he will too one day.

"It's not because I don't want to live in the village. It's because I have to go to a better place to find a better future, and the cities have more opportunities," he said.

Li Yikui spends his week at school and walks hours to his grandparents' farm on weekends. ( ABC News: Wayne McAllister )

Residency permit stops parents taking children

At the core of the left-behind phenomenon is the Chinese residency permit system called the hukou, which effectively stops parents from taking their children to the cities with them.

Public services like schools and hospitals can only be accessed where you live.

If you move, you have to pay — and for most factory workers that is way beyond their means.

Many workers also live in company dormitories and work shifts that leave no room for family life.

Hefeng county authorities want the central Government to reform the permit system.

"We need more attention on this issue," local official Mr Zhu Meiping said.

"A good solution would be to allow workers' children to go with them."

But to grasp the full extent of the plight of the left-behind kids you have to travel to where there is no help from the authorities.

In the town of Xichehe in the neighbouring Hunan province, 80 per cent of the children are growing up without parents.

From time to time, some parents return home to visit their children. But many are never seen again.

CCI has invited Foreign Correspondent to meet some of the most damaged kids.

"What they badly need is emotional support. There is nothing for them. They are blank," said Pan Yayun, a social worker with the group and a former left-behind kid herself.

About a third of the left-behind children — 20 million — will get involved in crime. ( ABC News: Wayne McAllister )

'I can't afford to raise you'

On the first day our team meets Xiang Ling, who at 14 is the primary carer in her household. She looks after her stroke-affected grandmother and her three younger cousins.

"I get up early to prepare simple breakfast and then go to school. And when I return home I wash clothes and prepare the dinner," she said, fighting back tears.

This has been her life since she was 10.

Just up the road an elderly woman is screaming at her 16-year-old granddaughter, Xie Bingxin, calling her useless and stupid.

"I'm telling you in front of these people: 'Don't stay in my house! I can't afford to raise you. Go and live in your own way'," she said.

The girl has been abandoned by her parents. CCI's Mr Lim will try to remove her for her own protection.

Mr Lim and Ms Pan rush to the house of another child who has been abandoned by his parents and is in the care of his grandmother.

Xiang Bao, 14, has announced he is leaving school to head for the city. They try to talk him around, but the boy's mind seems made up.

"I don't want contact," he told them.

Children are farmed out to grandparents or boarding schools or left to fend for themselves. ( ABC News: Wayne McAllister )

'You're of value,' charity tells children

The children's charity has built a drop-in centre to provide a safe place for the 200 children it supports.

Kids can get a bed, a meal or just talk. Elsewhere, efforts by authorities and Chinese NGOs to help the left-behind kids are mostly piecemeal.

Free meals and safe havens help. But what these children really need is emotional support.

Mr Lim said many become completely withdrawn after experiencing constant rejection and never knowing love. It takes years to build their self-esteem, if at all.

"We always tell them, 'You know, compared to any children outside, you're the same. You have a name, you're a human being. You're of value. We come here because we love you. And we value you as a human being'," he said.

Watch Generation Left Behind on iView.