Increased sophistication of data systems now allows for student achievement to be tracked and, in some states, linked to individual teachers. Further, rather than looking simply at student end-of-year achievement test scores in isolation, current statistical methods allow for analysis of student growth over time. These advances show promise for use in teacher evaluation by attempting to control for non-teacher related factors, such as a student's level of proficiency upon entering a classroom. These data systems and statistical methods enable researchers to revisit assumptions about the predictive value of teacher input factors as a means of ensuring high quality and effectiveness. This issue of "The Progress of Education Reform" highlights recent research that attempts to explore the relationship between traditionally accepted measures of teacher quality--teacher certification and in-class performance--and teacher effectiveness as assessed through student academic performance. It also includes links to additional resources on teacher quality and teacher evaluation methods.