Because We Said So
These people just make shit up. Read this:
So, where do we start? With the basics. As President Obama has emphasized, the single most important factor determining whether students succeed in school is not the color of their skin or their ZIP code or even their parents' income -- it is the quality of their teacher.That's in ideological position based on a willful disregard for the entire history of research on academic achievement, which clearly shows that the most enduring, persistent, and reliable predictor of achievement is socioeconomic status. Krashen's been compiling these research summaries for decades.