This study uses longitudinal data from Mexico's Carrera Magisterial teacher incentive program to identify teacher attributes that are positively associated with student test scores and to describe how teachers with these attributes are distributed across schools in two diverse Mexican states, Aguascalientes and Sonora. I find that teachers' scores on tests or training evaluations are significantly and positively related to student achievement in both states, while education levels and experience are not. In both states, teachers with higher scores on tests and training evaluations are more concentrated in urban schools and lower-poverty municipalities. These results have important implications for education systems attempting to professionalize their teacher workforces, as well as those seeking to ameliorate urban/rural disparities in educational quality. (Contains 1 figure, 6 tables, and 8 footnotes.)