ContextThe desire to provide useful, research-based information to policy makers and teachers poses a series of challenges for education researchers. These challenges include striking a balance between complexity and simplicity in the portrayal of teaching, addressing the potential conditional nature of what constitutes quality teaching, and appreciating the multiple perspectives by which quality teaching might be judged.PurposeThis article uses a mixed-methods approach to discuss these three challenges. We describe our own attempts to address these challenges in a longitudinal study of reading and mathematics instruction in fourth- and fifth-grade classrooms in moderate- to high-poverty schools, provide a mixed-methods analysis to identify the conditional nature of quality in teaching, report our results, and discuss implications for future studies of teaching.Research DesignWe focus on data that examined mathematics instruction in fourth and fifth grades during the 2004–2005 school year, including student academic records, observations about mathematics lessons, teachers’ curriculum logs, and interviews with teachers about the challenges that they face in providing quality instruction to their students. After limiting the data to students with scores on the state-mandated assessments, we had a total of 1,074 students taught by 63 different teachers in 66 different classes in the analytic sample. We examine the effects of teacher instructional practices on student achievement in classrooms with moderate and high levels of children from low-income families, using multilevel modeling; we then use interviews with teachers and specialists to better interpret the results of the quantitative analysis.ConclusionsWhat constitutes quality teaching, at least as judged by achievement gains, is contingent on students’ instructional needs. Although students in classes where teachers reported greater variability in the number of curriculum topics covered had lower levels of achievement, the effects of teacher actions and lesson content depended on the poverty status of the class. Examination of the qualitative data suggests that an important indicator of quality is the ability of teachers to navigate successfully the policy environment for their stu-dents—in this case, the ability to meet the demands of a newly implemented curriculum and the assessment timeline— and still present students with a coherent and appropriate set of lessons. Our analysis also indicates that students in majority-poverty classes are more dependent on their teachers to mediate the curriculum and provide multiple representations of mathematics, whereas students in moderate-poverty classes are better able to access mathematical knowledge through textbooks, standard worksheets, and more complex lesson content. A mixed-methods approach to studying teaching increases the likelihood of capturing the complexity of teaching but also highlights the importance of balancing complexity with the need for useful information for policy makers and practitioners.