Hu Zhongping dreams that one day his young sons may go to university and escape his life of casual manual labour. The aspiration seems increasingly unrealistic. Right now, he would settle for them going to school. Chinese children are entitled to a state education, but not all of them get one. And the tens of millions born to migrant workers like Hu are among the most vulnerable, owing to a registration system that divides the country's citizens into rural and urban dwellers, and dictates their rights accordingly.