Pretty and smart, the Beijing first-grader has nonetheless become a nightmare to her doting parents. "Weiwei turns on the television to watch cartoons after doing only 15 minutes of homework," complains her father. "She eats lots of chocolate but hardly touches her meals." Last May, in full sight of her guests, Weiwei, 7, imperiously scraped off for herself all the icing on her birthday cake. When her father scolded her, she snapped, "You're a monster and a fat pig!"
There may be hundreds of thousands, perhaps millions, of Weiweis throwing tantrums throughout China. The reason: Beijing's stringent one-child-per- couple policy. As...