High-stakes standardized testing (No Child Left Behind, 2002) will accurately measure school quality and drive improvement in student achievement.

No Child Left Behind was signed by President Bush on January 8, 2002, with bipartisan support that seemed remarkable in retrospect, Ted Kennedy was at the signing ceremony. The law required annual testing of students in grades three through eight in reading and math, mandated that all schools demonstrate "adequate yearly progress" toward full proficiency by 2014, and attached real consequences to failure: schools that repeatedly missed targets faced sanctions including restructuring, state takeover, or conversion to charter schools.

The theory was straightforward and, to its advocates, obviously correct: measure student performance rigorously, hold schools accountable for results, and the pressure of accountability would drive improvement. If schools knew that test results had consequences, they would find ways to improve them. The mechanisms of improvement were left to local discretion; the law specified the goal and the incentive.

The documented effects of a decade of implementation were considerably more mixed than the theory predicted. "Teaching to the test", narrowing instruction to the specific content and format of state assessments, was widespread enough to have been documented in hundreds of research studies. Schools in danger of sanctions reduced time spent on science, social studies, art, music, and physical education to concentrate on tested subjects. The research literature on whether this trade-off improved actual learning was at best ambiguous.

The "adequate yearly progress" measure proved structurally flawed. Because it required all subgroups within a school, including students with disabilities and English language learners, to meet the same proficiency thresholds on the same timeline, schools serving diverse populations were disproportionately labeled as failing regardless of whether their students were actually improving. By 2011, Education Secretary Arne Duncan estimated that 80 percent of American schools would be labeled failures under the law's formula. States had responded by setting their proficiency standards lower so schools could pass them.

NCLB was effectively replaced by the Every Student Succeeds Act in 2015, which shifted accountability decisions back to states and reduced the federal role in school sanctions. The high-stakes testing that the law had centered remained, but the specific accountability architecture was abandoned as unworkable. A generation of students whose education had been shaped by the law's assumptions graduated into a labor market without ever having had the breadth of instruction the testing had squeezed out.