In other words, the effect of good teaching is cumulative, but it is not compensatory. The findings converge consistently on one stunningly clear fact. The most important variable in improving student learning is the quality of the teacher. I do not want to leave you with the impression that other factors, such as socioeconomic status, or race, do not make a difference. In poor schools, pupils are much more likely to encounter less effective teachers than pupils in affluent schools.
Black pupils are more likely to be assigned to less effective teachers than white pupils are.
But, irrespective of race or socioeconomic condition, when pupils encounter highly effective teachers, they show remarkable gains. When all factors are controlled, it is the quality of the teacher that makes the difference in student learning. Teacher quality is more important than any other variable. And that brings me to my second point. The answer is, we are.