What makes for an effective teacher? Amanda Ripley, writing in the The Atlantic, describes the difference a teacher can make, by comparing two classrooms in two public elementary schools in the poor section of Washington, DC:
[School A] After a year in Mr. Taylor’s class, the first little boy’s scores went up—way up. He had started below grade level and finished above. On average, his classmates’ scores rose about 13 points—which is almost 10 points more than fifth-graders with similar incoming test scores achieved in other low-income D.C. schools that year. On that first day of school, only 40 percent of Mr. Taylor’s students were doing math at grade level. By the end of the year, 90 percent were at or above grade level.
[School B] As for the other boy? Well, he ended the year the same way he’d started it—below grade level. In fact, only a quarter of the fifth-graders at Plummer finished the year at grade level in math—despite having started off at about the same level as Mr. Taylor’s class down the road.
The rest of the article is about how Teach for America, an organization that trains people to work in high-poverty urban schools, selects candidates. If you’re not familiar with the organization–and even if you are–Ripley’s article is worth reading. The organization is relentless in measuring teacher effectiveness. It uses data to either confirm its ideas or, when the real world results don’t conform to their ideas, reevaluate itself.