Many of them can't walk home from school. As the article says, most students now live too far away from school (greater than three miles), and many rural/suburban areas have underdeveloped sidewalks and traffic systems.

If three miles sounds like not a big deal, it certainly is when you have short legs, a backpack full of books, and uncooperative weather. I was lucky enough to walk to/from school for most of my schooling. It was only around one mile and it still took 30 minutes. As an adult I would probably balk at a 90-minute commute.