The Gates Foundation has funded several large-scale studies in an attempt to get a better sense of the relationships among various measures of teacher quali cations, characteristics, and instructional practices (Gates Foundation, 2010). When the results of those studies are compiled, it should be possible to get a more accurate and nuanced view of the relationship among teacher quali cations, characteristics, practices, and student achievement growth. These studies include several observation instruments, tests of teachers’ knowledge for teaching in particular subjects, measures of teacher self-ef cacy, student surveys, student work samples, pre-and posttests, standardized achievement tests, and more. In recent years, researchers from around the world have demonstrated that there are large differences in the quality of teaching as evidenced by student achievement linked to speci c teachers. However, much less is known about the underlying reasons for those differences. The future of research in this area will be in the complex, classroom-level work of sorting out what makes some teachers more effective than others.