In Shanghai, such flats are regarded as an expensive ticket to a top primary school.

However, some of the children, despite having the required residential registration, have been denied admission since their family's home is not within the catchment areas of the schools their parents want them to enter.

Some parents are stunned to discover that other children living in the same neighbourhood are accepted by a school while theirs are rejected.

The decision as to which homes fall within a school's catchment area rests with the schools themselves and with education officials, who technically allocate pupils to public schools based on supply and demand. But in a country where urban families are officially limited to having one child, and where the national obsession with education starts barely after a child begins to walk, it is a system open to abuse.

Many angry and disappointed parents contend that schools and education officials are abusing their power and taking bribes.

At least three teachers knowledgeable about school admissions told the South China Morning Post that there was a thriving 'grey market' in which powerful officials make a lucrative but illegal sideline by selling admissions - often for 50,000 yuan or more - to top primary schools.

Normally, schools reserve a certain number of places for children of families without a hukou in the area, but these are often traded in the grey market.

Well-placed education officials and teachers often exploit the scarcity of places in leading schools to make fortunes from young parents desperate to give their child the best possible education.

But even if parents come up with the large sums involved for such back-door school placements, it is no guarantee of success.

Some parents must spend months or even years to find a trusted go-between with the right connections to powerful officials to transfer the money to them.

Teachers and officials often reject such deals if they don't trust the go-between who handles the transaction.

It is believed that the grey market is much bigger than thought, and in some cases involves property developers in the early phases of construction of big housing complexes.

One developer paid 'a large sum' to education officials to have houses under construction included in the catchment area for the Pudong Jianping Experimental Primary School.

The developer's efforts paid off, and his flats sold easily amid a buying frenzy by young parents.

According to one homeowner, the developer of their site admitted, frankly and publicly, that the cost of bribes for education officials had to be passed on to the buyers.

The one-child policy, in force since the late 1970s, is regarded by many as the root cause for parents' and grandparents' irrational obsession with their child's education.

Children today are expected to excel in subjects and skills ranging from English to painting and playing the piano before they enter elementary school.

More insidiously, some parents, through desperation or naked ambition, teach their children how to cheat their way into an elite school and through the public examination system.

At some private schools that don't require students to have a local hukou, parents are willing to bribe teachers for questions and answers to exams.

Admission to primary and junior middle schools is supposed to be free. Nonetheless, education costs have soared.

It is not uncommon for private schools to charge fees of more than 30,000 yuan a year, about two-thirds of an average wage earner's annual salary.

Anecdotal evidence shows that nearly all parents give teachers cash or prepaid expense cards during festivals, which the teachers accept.

Indeed, many students often remind parents to give their teachers lai see packets when a festival is nigh.