The metro areas include a great deal of sprawl where the schools (and even the drugstores) are separated from residential subdivisions by several miles of fast roads with no sidewalks or bike lanes.

Look for the percentage who actually live in the cities, vs. the metro areas.

I live in the District of Columbia, call it three miles from downtown. The high school students in the neighborhood who are in public schools attend Wilson High School or one of the district's magnets, namely School Without Walls and Banneker. Banneker might be a mile and a half away, Wilson and Walls are more like four miles. I will say that it appears to me that most of them take public transportation to and from school.

And when I lived in the Denver suburbs, my brother attended a couple of county schools. The junior high was at least a couple of miles away, the high school more like five. Do not underestimate American sprawl.