"Campbell's Law," that is. The late social scientist Donald Campbell's idea: "The more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor."
Examples of Campbell's Law at work (as summarized by Richard Rothstein here) include "when cardiac surgeons, held accountable for raising surgical survival rates, refuse to operate on the sickest patients most in need of intervention; when employment agencies held accountable for job placement numbers meet their quotas by placing the unemployed only in the most easily filled and lowest-skill jobs; when colleges send pre-completed applications to unqualified high school students because U.S. News & World Report ranks college selectivity by the number of applicants rejected; or when Wall Street traders take reckless risks because they are rewarded only for short-term, easily measured outcomes."
Campbell himself saw how his principle would inevitably apply to the use of high-stakes testing in education: "[A]chievement tests may well be valuable indicators of general school achievement under conditions of normal teaching aimed at general competence. But when test scores become the goal of the teaching process, they both lose their value as indicators of educational status and distort the educational process in undesirable ways. . . . Achievement tests are, in fact, highly corruptible indicators."
In other words, test-driven education is likely to have unintended consequences. That's part of what drove Diane Ravitch to change her mind about No Child Left Behind. It's worth noting, though, that although those consequences may have been unintended, they certainly weren't unforeseeable. Campbell formulated his "law" in 1976, and others (for example, Peter Sacks) were applying it to high-stakes testing long before Ravitch finally came around on the issue.
..How can I comment?