The Obama administration has worked hard to strengthen public-school teaching—a $400 billion-plus workforce, and perhaps the single strongest lever in schools for raising student achievement. But just after Thanksgiving, the president signed a major new education law that largely abandoned the cornerstone of his teacher agenda: pressing states and school districts to take more seriously the task of identifying who in the profession was doing a good job, and who wasn’t.Two powerful forces at opposite ends of the political spectrum had attacked the president’s strategy—teacher unions wanting to end the new scrutiny of their members and Tea Party members targeting the Obama plan as part of a larger anti-Washington campaign. As a result, the new Every Student Succeeds Act terminates the Obama administration’s incentives for states and school districts to introduce tougher teacher-evaluation systems. And the law effectively bans the U.S. Secretary of Education from promoting teacher-performance measurements in the future.