For public schools, that represents a loss of about 4% of their enrollment.

Expect the exodus to grow larger, as the United States is undergoing a major change in philosophy regarding publicly-funded K-12 education, away from funding government-run school systems and toward funding individual students—with parents getting to choose where their children learn.

In June, Arizona put itself at the leading edge of that shift: Every Arizona family can now direct about $7,000 a year per student toward the education solution of their choice. Funds can be used for private schools, home schooling, tutoring and online learning.

Arizona also provides free choice among public schools—rather than being forced into a particular school by neighborhood, parents who prefer public schools can pick whichever one they want, first-come first-served.

Defenders of the status quo typically characterize school-choice laws as "taking money away" from public schools, recoiling at the very idea that government money would be spent anywhere other than a government institution.

However, that's already how the great majority of publicly-funded education and other entitlements work, without uproar.