All teachers (N = 32) at one middle school participated in a university-led intervention to improve student engagement. Teachers discussed four principles of motivation and related instructional strategies. Teachers enacted instructional strategies in their classrooms. We observed six randomly selected teachers and their students over 3 years. Analyses of the dynamic patterns of teacher-student interaction (using an application of state space grids) revealed two distinct patterns. The upward group (n = 3) showed an increase of teacher motivational support and student engagement. The stable group (n = 3) demonstrated low levels of both teacher motivational support and student engagement. Qualitative analyses of instructional differences between the two groups help explain student engagement. Implications include conceptualizing student engagement as interpersonal classroom activity and measuring change as developmental and dynamic phenomena.