The second and even the third generation of migrant workers' children have grown up, but the country's more than half-century-old hukou (household registration) system, and the rules based on it, has remained unchanged.

Most migrant workers are required to send their sons and daughters back to their place of residence to take the college entrance examination (gaokao), even though that place may mean nothing to them. Most of such children grow up in the cities where their parents work, and only the hukou booklet they carry tells them where they officially belong.

An increasing number of people see the hukou system as the caste system of China. Since only people carrying the right hukou have full access to public services available in one place, those with rural hukou are denied the rights to get education and medical treatment, and own a house in cities.

This discriminative system drives children of migrant workers to the countryside to take the gaokao on the pretext that their household registration says they are rural residents. The real reason for requiring migrant workers' children to take the gaokao in the place of their hukou is to prevent "outsiders" from cutting into the "real" urban residents' chances of getting admission to good universities.

Chinese universities allot admission quotas to different provinces and cities. Since their presence is a challenge to their "local" peers, migrant workers' children are often unwelcome wherever they take the gaokao.