If it were not for his big appetite, the world may never have known Yao Ming.

His parents - both former basketball players - found it increasingly hard to feed their meat-loving son on their meagre income. At the age of nine, the hulking boy was already 1.7m tall.

So although he was not keen on shooting hoops, his parents enrolled him in a sports school in Shanghai, where they knew he would get decent meals and a bottle of his favourite milk daily. There, he honed the skills that eventually made him an NBA All-Star.

"I was bribed into becoming a basketballer," Yao Ming had jokingly told the Chinese press.

Such stories were commonplace in China during the 1980s and 1990s when sports schools sometimes provided a way out for children from impoverished families.

But the system which provides most of China's Olympians is faltering, with the country's growing wealth and a greater reluctance by parents to subject their offspring to the punishing regime of sportsmen.

Besides Yao Ming, China's sports schools have groomed the country's most famous Olympians, such as hurdler Liu Xiang, gymnast Li Ning and shuttler Lin Dan. Several went on to become national coaches, including table tennis world champion Liu Guoliang and volleyball star Lang Ping.

But others have fallen by the wayside, most notably former national team gymnast Zhang Shangwu, who slipped into a life of crime after an injury cut short his sporting career in 2002.

He made the headlines after he was found living in the streets in 2011, performing acrobatics in Beijing's subway for handouts.

The plight of athletes like Zhang, who spent most of his time training from the age of five, is part of the reason for the declining number of sports schools.

As a result, some of China's sports stars have led the call for schools to set aside more classroom time for sports.

Among those championing an equal focus on education and sports is former table tennis star Liu Wei, who began training in a Shandong school at 11. She returned to school to get a degree only after 16 years of provincial and national training.

'For the individual, switching to such a system... is more humane," she told Xinhua in April.

"Then the children won't miss their best age to study. In the future, they won't be a burden on society either."