We estimate the importance of teachers in Chicago public high schools using matched student-teacher administrative data. A one standard deviation, one semester improvement in math teacher quality raises student math scores by 0.13 grade equivalents or, over 1 year, roughly one-fifth of average...

We match administrative data on Chicago public high school students and teachers at the classroom level to estimate the importance of teachers to mathematics test score gains. We show that sampling variation and other measurement issues are important drivers of naïve estimates of teacher...