Increased attention has been given to learning trajectories (LT) as structural frameworks for educational instruction. The purpose of this study was to explore preschool teachers' descriptions of self-change, seven years after the start of their participation in LT-based professional development and instruction. This study was part of a larger study to test the effects of a model for scaling up educational interventions also based on LT. We used grounded theory methodology to study teachers' descriptions of self-change. The dominant change was teachers' newly acquired awareness of the mathematical capabilities of preschoolers. Teachers' ability to notice these capabilities was scaffolded by their knowledge and use of LT in implementing the mathematics curriculum, but change occurred as the teachers noticed, listened to, and elicited talk from the children. In brief, teachers learned from the children. Teachers appeared to be on their own trajectories of learning, as they began to build mental models of their children's mathematical thinking. Together, these trajectories may provide a theory of teacher learning.