HANJING, China — Wu Yiebing has been going down coal shafts practically every workday of his life, wrestling an electric drill for $500 a month in the choking dust of claustrophobic tunnels, with one goal in mind: paying for his daughter’s education.

His wife, Cao Weiping, toils from dawn to sunset in orchards every day during apple season in May and June. She earns $12 a day tying little plastic bags one at a time around 3,000 young apples on trees, to protect them from insects. The rest of the year she works as a substitute store clerk, earning several dollars a day, all going toward their daughter’s education.

Many families in the West sacrifice to put their children through school, saving for college educations that they hope will lead to a better life. Few efforts can compare with the heavy financial burden that millions of lower-income Chinese parents now endure as they push their children to obtain as much education as possible.

Yet a college degree no longer ensures a well-paying job, because the number of graduates in China has quadrupled in the last decade.

Mr. Wu and Mrs. Cao, who grew up in tiny villages in western China and became migrants in search of better-paying work, have scrimped their entire lives. For nearly two decades, they have lived in a cramped and drafty 200-square-foot house with a thatch roof. They have never owned a car. They do not take vacations — they have never seen the ocean. They have skipped traditional New Year trips to their ancestral village for up to five straight years to save on bus fares and gifts, and for Mr. Wu to earn extra holiday pay in the mines. Despite their frugality, they have essentially no retirement savings.

Thanks to these sacrifices, their daughter, Wu Caoying, is now a 19-year-old college sophomore. She is among the growing millions of Chinese college students who have gone much farther than their parents could have dreamed when they were growing up. For all the hard work of Ms. Wu’s father and mother, however, they aren’t certain it will pay off. Their daughter is ambivalent about staying in school, where the tuition, room and board cost more than half her parents’ combined annual income. A slightly above-average student, she thinks of dropping out, finding a job and earning money.

“Every time my daughter calls home, she says, ‘I don’t want to continue this,’ ” Mrs. Cao said. “And I say, ‘You’ve got to keep studying to take care of us when we get old’, and she says, ‘That’s too much pressure, I don’t want to think about all that responsibility.’ ”

Ms. Wu dreams of working at a big company, but knows that many graduates end up jobless. “I think I may start my own small company,” she says, while acknowledging she doesn’t have the money or experience to run one.

For a rural parent in China, each year of higher education costs six to 15 months’ labor, and it is hard for children from poor families to get scholarships or other government financial support. A year at the average private university in the United States similarly equals almost a year’s income for the average wage earner, while an in-state public university costs about six months’ pay, but financial aid is generally easier to obtain than in China. Moreover, an American family that spends half its income helping a child through college has more spending power with the other half of its income than a rural Chinese family earning less than $5,000 a year.

It isn’t just the cost of college that burdens Chinese parents. They face many fees associated with sending their children to elementary, middle and high schools. Many parents also hire tutors, so their children can score high enough on entrance exams to get into college. American families that invest heavily in their children’s educations can fall back on Medicare, Social Security and other social programs in their old age. Chinese citizens who bet all of their savings on their children’s educations have far fewer options if their offspring are unable to find a job on graduation.

The experiences of Wu Caoying, whose family The New York Times has tracked for seven years, are a window into the expanding educational opportunities and the financial obstacles faced by families all over China.

Her parents’ sacrifices to educate their daughter explain how the country has managed to leap far ahead of the United States in producing college graduates over the last decade, with eight million Chinese now getting degrees annually from universities and community colleges.

But high education costs coincide with slower growth of the Chinese economy and surging unemployment among recent college graduates. Whether young people like Ms. Wu find jobs on graduation that allow them to earn a living, much less support their parents, could test China’s ability to maintain rapid economic growth and preserve political and social stability in the years ahead.

Leaving the Village

The ancient village of Mu Zhu Ba is perched on a tree-covered crag overlooking a steep-sided mountain gorge in southwestern Shaanxi province, deep in China’s interior, 900 miles southwest of Beijing. The few scarce acres of flat land next to a stream on the valley floor were reserved until recently for garden-size plots of rice, corn and vegetables.

Villagers were subsistence farmers. Every adult and all but the youngest children worked from dawn to dusk, planting, weeding, hand-watering and harvesting rice, corn and vegetables to feed themselves. They also built and maintained three-foot-wide terraces where the sides of the valley began to curve upward before turning into vertiginous, forested slopes that soared into the clouds.

The relentless work left little opportunity for education. Mrs. Cao, now 39, learned to read some Chinese characters at first- and second-grade classes conducted in her village. But later grades were taught at a school in a larger village at the other end of the valley, a seven-mile walk away, and Mrs. Cao dropped out in third grade.

Her husband, now 43, grew up in a similarly poor village on the other side of the mountain and did not attend school at all.

They married early, and Mrs. Cao had just turned 20 when she gave birth to Ms. Wu. The couple earned just $25 a month. As their baby grew into a toddler, they began worrying that she would inevitably drop out of school early if she had to walk so far to classes every day. So like hundreds of millions of other Chinese over the last two decades, they decided to leave their ancestral village and their families.

“All the parents in the village want their children to go to college, because only knowledge changes your fate,” Mrs. Cao said.

By the time Ms. Wu reached middle school, the crystalline mountain air of Mu Zhu Ba was a dim memory. The family had moved to Hanjing, a coal mining community on the plains of northern Shaanxi province, nearly 300 miles northeast of their ancestral village.

A Coal Miner’s Daughter

Mr. Wu built the family’s two-room brick house himself. They bought their first small refrigerator, a coal stove and a used stereo, and a bare light bulb for the living room and another for the bedroom.

The house, on the town’s rural outskirts, was across a two-lane paved road from a small coal mine where Mr. Wu learned to maneuver a shoulder-carried, 45-pound electric drill in narrow spaces far under the earth, working long shifts and coming home covered with coal dust. He earned nearly $200 a month then, providing more money to educate their daughter. In the family bedroom, where calendar posters of the actress Zhang Ziyi had been plastered on the wall for extra insulation, Mrs. Cao carefully kept all of her daughter’s school papers. Wu Caoying was in seventh grade, but her village school was already teaching her geometry and algebra at a level beyond most American seventh graders. She was also studying geography, history and science, filling homework notebooks with elegant penmanship.

The problem was English, an increasingly important subject for students who wanted to qualify for anything but the worst universities.

The village had an English teacher, and Ms. Wu started learning the language in fourth grade. But then the teacher left, so she was not able to study English during fifth and sixth grade.

Ms. Wu resumed English classes in the seventh grade, but her mother was concerned and began hiring substitute teachers as English tutors for her daughter.

Mrs. Cao said that she was convinced that this would help her daughter become the first in the family to attend college. “If we had not come here, she would have needed to stay home, to help cook and cut wood,” Mrs. Cao said.

But their financial sacrifices were only beginning.

For high school, Wu Caoying began attending a government-run boarding school two miles from the family’s house. Many high schools in China are boarding schools, an arrangement that allows local governments to impose hefty fees on parents. Tuition was $165 a semester. Food was $8 a week. Books, tutorials and exam fees were all extra.

Boarding School

Ms. Wu and seven other teenage girls had bunk beds in a cramped dormitory room. She dressed better than the other girls, in a tight blue coat her mother had just given her for Chinese New Year.

She woke at 5:30 every morning to study, had breakfast at 7:30, then attended classes from 8:30 a.m. to 12:30, 1:30 to 5:30 in the afternoon and 7:30 to 10:30 in the evening. For entertainment, there were occasional showings of patriotic movies. She studied part of the day on Saturdays and Sundays. But she also joined a volunteer group that visited the elderly — social work that might help on a college application in the United States but not in China, where the national entrance exam for universities is all-important.

Mr. Wu no longer worked at the coal mine across the street, which had been closed because of a combination of safety regulators’ concerns and depletion of the coal seam. He had become a migrant once more, taking a job 13 hours away by train at a coal mine in a northern desert. Mr. Wu worked 10-hour shifts up to 30 consecutive days. Safety standards were lower at the new mine, in an industry that kills thousands of Chinese miners in industrial accidents each year and maims many more.

The new job, however, allowed Mr. Wu to double his income, and he brought back his pay every two months to his wife to pay for their daughter’s education.

Their main worry was their daughter’s academic performance; they thought she did not study hard enough. “She likes to talk to boys, although she doesn’t have a boyfriend,” Mrs. Cao said.

Their daughter ranked 16th in her class of 40, respectable but not good enough in their eyes. But they despaired of being able to help Ms. Wu when she came home on weekends. “We just have an elementary school education. We don’t really know what she’s studying,” Mrs. Cao acknowledged.

Sitting at home while his daughter was at boarding school one day several years ago, Mr. Wu said he was so disappointed with his daughter’s performance that he would not mind if she dropped out, caught a train to Guangdong province, 30 hours away on the coast and took an assembly line job at a factory.

Odds Against Rural Youths

As Ms. Wu approached the national higher-education entrance exams in the spring of 2011, the odds were stacked against her, and heavy costs loomed for her parents as a result.

Youths from poor and rural families consistently end up paying much higher tuition in China than children from affluent and urban families. Yet they attend considerably worse institutions, education finance specialists say.

The reason is that few children from poor families earn top marks on the national exams. So they are shunted to lower-quality schools that receive the smallest government subsidies.

The result is that higher education is rapidly losing its role as a social leveler in China and as a safety valve for talented but poor youths to escape poverty. “The people who receive higher education tend to be relatively better off,” said Wang Jiping, the director general of the Central Institute for Vocational and Technical Education in China.

Top four-year universities in China have resisted pressure to expand enrollments. So roughly half of all college students now attend a growing number of less prestigious three-year polytechnics instead.

The polytechnics resemble community colleges in the United States, but they offer more specialized vocational training and fewer general-knowledge courses like history or literature.

Affiliated with provincial and local governments or run by private businesses, polytechnics charge up to twice as much tuition as top universities, which are owned, operated and heavily subsidized by the central government. Despite high tuitions, the polytechnics spend much less teaching each student than universities because they receive so few subsidies.

While the central government offers extensive, need-based grants and loans for students at four-year universities, little financial aid is available for students at polytechnics to help pay higher tuitions. Yet students at polytechnics tend to be from poor or rural backgrounds. China’s education ministry said last year that 80 percent of students at polytechnics were the first in their families to go into higher education.

The national entrance exam heavily favors affluent urban children. Top universities, concentrated in Beijing and Shanghai, give preference to local high school students, admitting them with lower exam scores than students from elsewhere. Rural students have to score higher to get in.

That is doubly difficult because a crucial section of the exam tests competence in a foreign language, almost always English. Rural schools like Ms. Wu’s struggle even to find English teachers.

Most students at Peking University, one of the country’s most prestigious, come from such affluent backgrounds that researchers last summer had to suspend a long-running survey that rewarded students with second-class train tickets if they would write about changes in their hometowns. The students began refusing to write the essays because they were not interested in second-class tickets, preferring costlier seats on new bullet trains.

For Ms. Wu, coming from a less affluent family, the challenge of getting into a top university would prove too great.

Student in a Big City

Ms. Wu passed the national college entrance exam, but just barely.

She scored 300 points out of a possible 750, slightly above the 280 threshold for being allowed to attend an institution of higher education. It was far below the 600-plus scores needed for the nation’s finest four-year universities. So she attends a polytechnic in the metropolis of Xi’an, the capital of Shaanxi province.

What tripped her up on the exam was her weakness in English. By contrast, she did well in Chinese and other subjects.

Her elementary school back in Hanjing has now begun teaching English starting in kindergarten, she said, adding that she hoped the next generation would fare better on the national test.

Ms. Wu has tried, unsuccessfully so far, to do well enough in classes at her polytechnic to transfer to an affiliated, four-year university, where the tuition is 25 percent lower.

The Chinese government offers a few scholarships for polytechnic students, but they are distributed mostly based on grades, not financial need. Top students, often from more affluent families who could give them more academic support during their formative years, receive grants that cover up to three-quarters of their room and board.

Average students like Ms. Wu pay full cost and hear frequent complaints from their parents. “I tell my daughter to study harder so she can reduce the school fees,” Mrs. Cao said.

But studying is almost all that Ms. Wu does. She says she still has no boyfriend: “I have friends who have boyfriends and they argue all the time. It is such a hassle.”

The big question for Ms. Wu and her family lies in what she will do on graduation. She has chosen to major in logistics, learning how goods are distributed, a growing industry in China as ever more families order online instead of visiting stores.

But the major is the most popular at her school, which could signal a future glut in the field. That is a sobering prospect at a time when young college graduates in China are four times as likely to be unemployed as young people who attended only elementary school, because factory jobs are more plentiful than office jobs.

Ms. Wu realizes the odds against her. Among those who graduated last spring from her polytechnic, she said, “50 or 60 percent of them still do not have a job.”

Mrs. Cao is already worried. The family home across the road from the abandoned coal mine is starting to deteriorate in the wind and acrid pollution, and they have scant savings to rebuild it. Her husband has been able to move home after being hired at a new mine in Hanjing as a drilling team leader. The extra responsibility allows him to almost match his pay at the desert coal mine, but at his age carrying a heavy drill is becoming more difficult, and he won’t be able to continue doing hard labor forever. Their daughter is the parents’ only hope.

“I’ve only got one, so I have to make sure that one takes care of me when we get old,” Mrs. Cao said. “My head is killing me with thinking, ‘What if she can’t get a job after we have spent so much on education?’ ”

A version of this article appeared in print on February 17, 2013, on page A1 of the New York edition with the headline: In China, Betting It All on a Child in College.