Teachers' classroom management practices are an essential aspect of supporting student engagement, yet they often vary in response to changing conditions in the classroom. This study explored the variability within middle school teachers' observed practice and their students' engagement as a function of contextual factors. Observers visited teachers (n = 278) on three occasions, typically over the course of two consecutive school days using two consecutively-administered observational tools (n = 1582 total observations). Multilevel regression models and multiple comparison adjustments suggested teachers' emotional support and student cooperation declined over time during the morning hours. Small group work, individual seat work, and "other" instructional groupings were often associated with less desirable outcomes than whole group instruction. Finally, most teacher practice and student engagement outcomes were rated more favorably when observers perceived a larger proportion of the students in the classroom to be White. Implications are discussed for observational measures in research and practice and for improvements in teachers' classroom management practices, particularly when working with students of color.