Teachers play a large role in determining whether or not the classroom climate experienced by students is positive, especially through their visible emotional behaviors (i.e., neutral, positive, and negative emotional expressions). Research suggests that teachers make specific contributions to the classroom emotional climate in actions such as building relationships with students, managing classroom behaviors, and displaying enthusiasm during instruction. The current study explored one specific contribution teachers make to the classroom emotional climate (i.e., teacher displayed affective demeanor) likely associated with maintaining student engagement. The purpose of this study was to capture the unique influences of teacher displayed affective demeanor as it relates to students' engagement. Secondary analysis using video recordings of 84 first through third grade classrooms were used to explore teachers' displayed affective demeanor (n = 79) and students' off-task behavior (n = 539) during reading instruction. Limited research addresses the contribution of teacher displayed affective demeanor as students progress through elementary school and move to new classrooms. This study investigated these associations both concurrently and longer term (across three school years). Specifically, multilevel growth models were used to explore whether and how teachers' affective demeanor and students' off-task behavior were associated over time. Two main research aims were addressed: (1) How does teachers' displayed affective demeanor relate to students' off-task behavior cross-sectionally in first, second, and third grade? and (2) How does teachers' displayed affective demeanor relate to growth in student off-task behavior from first through third grade? Teachers' demeanor characteristics were associated with students' off-task behavior and distinct associations between students' off-task behavior and teachers' demeanor were present in first, second, and third grade. Additionally, an increase in teachers' positive demeanor was associated with less off-task behavior in the spring of third grade and a more rapidly declining rate of growth in off-task behavior over time. The results suggested that first grade teachers' positive demeanor contributed to changes in students' off-task behavior in the same school year as well as the following two school years that students experienced in different classrooms. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]