Frederick Hess for the American Enterprise Institute: A new study by WalletHub has concluded that Philadelphia and Detroit are two of the nation’s top 10 “most efficient” school systems. Seriously. This illuminates one of the perils with “evidence-based” education — namely, the likelihood that data will be used in nonsensical ways and that foolishness will be passed off as evidence.

WalletHub analysts combined fourth- and eighth-grade test scores, spending data, and various socioeconomic controls to rank cities on cost-effective performance. In a truly bizarre move, however, they didn’t use per-pupil spending. Rather, they calculated cost efficiency based on per-capita spending (in other words, school spending per local resident.) This decision inflated the reported cost-effectiveness for those cities with lots of elderly residents (which helps explain why Miami, Ft. Lauderdale, and Orlando all finished in the top 15.)