Students in teacher Miguel Aguilar's fifth-grade class consistently make gains on standardized tests while next door, fifth graders who pass through teacher John Smith's class each year fall behind.

NPR: 'L.A. Times' Series Examines Teacher Ratings

Reformers cannot constantly wave this idea around as though they are the only ones who care about teacher quality, and then plug their ears whenever critics point out that tests are a very crude, very imprecise measure of student achievements and teacher quality.

FORBES: The False Choices of Education Reform

Posing as a teacher, Ternovskiy got access to some practice tests before they were delivered to his school.

NEWYORKER: Roulette Russian