From the introduction:
"Suburbanization and decisions about school siting are important determinants of why children now live so far from school. Historically, small neighborhood schools served as "anchors" within the community and places for after-school programs, for social and recreational gathering, and as disaster shelters.59 However, after the 1950s, many states established policies on the size and location of school buildings that influenced school siting. According to those guidelines, to receive state funding, schools had to have a minimum acreage (eg, elementary schools needed to be on at least 10 acres), and more students translated to larger required school-grounds size (eg, an extra acre for every 100 students). Because untapped acreage sufficient to meet these standards is most often at the edge of an urban area, neighborhood schools (typically only 2–8 acres in size) were frequently demolished or closed in favor of "big-box schools" at the outskirts of cities. Recommendations on school size from the Council of Education Facilities Planners International (CEFPI) were revised in 200461 and no longer recommend a minimum acreage. There is increasing interest in supporting smaller schools, but change to policies on school land size occurs slowly. It is also important to acknowledge that there may be some trade-offs to consider regarding school size and physical activity. There is some research suggesting that larger school campuses, buildings, and play areas may promote youth physical activity during the school day.
Distance is, of course, not the only barrier preventing children from walking or biking to school. A recent nationally representative study found that even among children who lived within 1 mile of school, less than half walk to school even 1 day/week."