This paper examines whether teachers in schools serving students from high-poverty backgrounds are as effective as teachers in schools with more advantaged students. The question is important. Teachers are recognized as the most important school factor affecting student achievement, and the achievement gap between disadvantaged students and their better off peers is large and persistent.

Using student-level microdata from 2000-2001 to 2004-2005 from Florida and North Carolina, the authors compare the effectiveness of teachers in high-poverty elementary schools (>70% FRL students) with that of teachers in lower-poverty elementary schools (<70% FRL students). The results show that the average effectiveness of teachers in high-poverty schools is in general less than teachers in other schools, but only slightly, and not in all comparisons. The authors also find differences in within-school-type variation in teacher effectiveness in nearly every comparison. These differences are largely driven by the longer tail at the bottom of the teacher effectiveness distribution in high-poverty schools. Teachers at the top of the effectiveness distribution are very similar across school settings. The observed differences in teacher quality between high-poverty and lower-poverty schools are not due to differences in the observed characteristics of teachers, such as experience, certification status and educational attainment. Rather, they appear to arise from differences in the marginal return or payoff from increases in a characteristic. In particular, the gain in productivity from increased experience is much stronger in lower-poverty schools. The lower return to experience in high-poverty schools does not appear to be a result of differences in the quality of teachers who leave teaching or who switch schools. Rather, it may be the case that the effect of experience on teacher productivity may depend on the setting in which the experience is acquired. If there are positive spillovers among teachers that depend on teacher quality (ie. teacher "peer effects") or if exposure to challenging student populations lessens the future productivity of teachers (i.e. leads to "burn out"), teachers in schools serving large proportions of low-income students may simply not improve much as time goes by. These findings suggest that solutions to the achievement gap between high and lower-poverty schools may be complex. Changing the quality of new recruits or importing teachers with good credentials into highpoverty schools may not be sufficient. Rather, the findings suggest that measures that induce highly effective teachers to move to high-poverty schools and which promote an environment in which teachers' skills will improve over time are more likely to be successful.