It has been 30 years since the May morning when Julie Patz, a Manhattan mother, finally allowed her 6-year-old son, Etan, to walk by himself to the school-bus stop, two blocks away. She watched till he crossed the street -- and never saw him again. Since that haunting case, a generation of parents and administrators have created dense rituals of supervision around what used to be a mere afterthought of childhood: taking yourself to and from school. Certain realities also shape these procedures, such as the schedules of working parents, unsafe neighborhoods and school transportation cuts.

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Parents' worst nightmares were inflamed recently by the re-emergence of Jaycee Dugard, the 11-year-old girl who was kidnapped on her way to the school bus 18 years ago in northern California. The fear of abduction by strangers "has become a norm within middle-class parental circles," said Paula S. Fass, a history professor at the University of California, Berkeley, and author of Kidnapped: Child Abduction in America. "We try to control our fears to the nth degree, so we drop our children off right at school. It's a confirmation that I'm a good parent.'"

In 1969, 41 percent of children either walked or biked to school; by 2001, only 13 percent still did, according to data from the National Household Travel Survey. In many low-income neighborhoods, children have no choice but to walk. During the same period, children either being driven or driving themselves to school rose to 55 percent from 20 percent. Experts say the transition has not only contributed to the rise in pollution, traffic congestion and childhood obesity, but has also hampered children's ability to navigate the world.