From a Wall Street Journal review by John Ketcham of the book by Philip K. Howard titled “Not Accountable: Rethinking the Constitutionality of Public Employee Unions”:

In 2008, six years after securing control over New York City’s public schools, Mayor Michael Bloomberg and schools chancellor Joel Klein put forward a program to tie teacher tenure to student performance. The goal was to reward the best-performing teachers with job security, encourage better student outcomes, and hold teachers accountable for demonstrated results. To most New York residents, it surely sounded like a good idea.