Since 2002, when the federal No Child Left Behind Act was signed into law, American public schools, and later their teachers, have been evaluated by the standardized test scores of their students.  States have been required to punish the schools with the lowest scores—firing their principals or some of their teachers, closing the schools, or turning them over to charter schools.  But the idea that we can judge schools and judge teachers by metrics—by the aggregate test scores of their students—evolved long before the passage of No Child Left Behind—even prior to the publication in 1983 of the A Nation At Risk report that is said to have begun the wave of standards-based school reform. Perhaps it has been part of growing enchantment with our society’s advancing capacity to collect and analyze data.

Today it is becoming widely acknowledged, however, that the strategy of test-and-punish didn’t improve public schools, didn’t…