Cui Weiping had become an adept cotton farmer and tractor driver in a bleak east China village in 1977 when college entrance exams were restored after the Cultural Revolution.

"It was a profound turning point in my life," said 51-year-old Cui, now a professor at the Beijing Film Academy.

Underground reading on the farm helped make Cui one of the 220,000 lucky ones -- out of a staggering backlog of 5.7 million candidates -- to get through that year's hastily held exams.

"We would get up to jog and study so early that the stars were still in the sky," she said of her life at Nanjing University. "Everybody wanted to win the lost time back."

This year, a record 10 million Chinese youngsters will sit the two-day National College Entrance Exam, starting on Thursday, vying for about half that number of university places.

The entrance exam -- commonly known as "gaokao" in Chinese -- is credited as the backbone of China's remarkable reform-era growth in the 30 years since it was restored, despite mounting criticism that it encourages rote learning and puts too much pressure on overburdened adolescents.

Nevertheless the annual rite, during which virtually the whole nation holds its breath, has turned people's lives around, for better or worse, over generations.

For students like Lai Yumei, gaokao is her best chance to climb the social ladder in a country with widening rich-poor and urban-rural gaps.

The sophomore at the medical school of the prestigious Peking University is from a mountain village in South China.

Her father died when she was young leaving her mother to raise her and her younger brother on earnings from a plot of rice in the impoverished southeastern province of Jiangxi.

"Since that time, relatives and neighbours told me to study hard and that getting into a university is the way out," Lai, 22, said.

That way out is only for the lucky few.

A study by Yang Dongping, an education expert at the Beijing Institute of Technology, found that the chance of a rural child making it to college could be a third of that of his or her urban peer, as the best teachers and resources in China's primary and secondary education are concentrated in the cities.

Intellectual Youth

In Cui Weiping's day, university was just a dream for most people.

One of the 17 million urban "intellectual youth" sent into the countryside to learn from the proletariat, Cui spent three years after high school farming in coastal Jiangsu.

The university entrance exams were broke up in 1966. Universities resumed partial recruitment in 1970, but only workers, farmers and soldiers were eligible through "recommendations".

Cui had welcomed hard labour in a bid for such a nomination.

"I was a good hand in the cotton fields at anything from sowing and weeding to spraying pesticides and harvesting," Cui recalled proudly.

These days she is more renowned for her translation of former Czech President Vaclav Havel's works on post-authoritarianism.

In the end, Cui did not get the chance to use her "good work performance."

The resumption of gaokao in 1977 was an important aspect of the reconstruction of a society devastated by political turmoil and anti-intellectualism, said Yang, the education expert.

"It reaffirmed the dignity of knowledge and education, something that is merely commonsense but that had been denied in a radical way," Yang said.

It was also significant in giving equal education rights back to groups that were once politically ostracised, he added.

Lai studied 13 hours a day in her last year of high school preparing for the exams, spending less than 3 yuan (40 cents) a day on food to save money.

"I would have ended up in a Guangdong factory if I didn't make it," the soft-spoken Lai said.

Guangdong is the booming southern province where the bulk of teenagers in Lai's hometown, including her brother, join the ranks of 20 million migrant peasant workers after middle school or even elementary school.

But for Lai, success in the gaokao meant a different future.

At her northwestern Beijing campus, where students mill around in trendy clothes and iPods in their ears, slightly built Lai wore a plain T-shirt and jeans. Three years of urban life have failed to lighten her sun-tanned skin, the mark of her rural upbringing.

Almost out of habit, she keeps her daily food budget under 7 yuan (90 cents), even though her annual tuition of 6,000 yuan is covered by government loans.

When she returns home for the Lunar New Year holiday, she gathers with her childhood playmates, now manual labourers in the factories of Guangdong, but their different paths through life have set the once close friends apart.

"I dare not talk about my college life," Lai said. "I just tell some jokes to avoid the awkwardness."