The aim of this study was to explore trajectories of teachers' instructional support as perceived by students during a national initiative to develop lower secondary schools. Grade eight and nine students (N = 815) from nine Norwegian schools participated in three waves of data collection within one-and-a-half academic years. Growth mixture model (GMM) techniques were applied to examine change over time in students' reports of instructional support, allowing the examination of the impact of change in subgroups characterized by different types of growth trajectories. To investigate the impact of improvements in instructional support on students' academic outcomes, course grade-differences in math were included. Latent-class growth modeling identified two trajectories of teachers' instructional support: (1) the "normative group" (90.5%) and (2) the "increasing group" (9.5%). The results indicated that there were no significant differences in math course grades between the groups. However, the two groups differed significantly in behavioral problems and motivation. Methodological considerations and implications for practice are discussed.