This study explores a spatial reasoning learning trajectory of a student with difficulty in mathematics. Using a teaching experiment methodology across 15 instructional sessions, we observed how the student responded to instruction based on an established 2D shape composition learning trajectory (Sarama & Clements, 2009). A narrative microgenetic analysis identified conditions that were likely to have promoted learning. The analysis shows the student's actual trajectory was similar to that of the hypothesized learning trajectory. Challenges to progress emerged around teacher-guided components of instructional support. We describe how a student-centered approach and mathematizing through specific praise was generative of learning, while explicit guidance was not. We discuss how the guiding conjecture of the teaching experiment evolved and how it is situated within the broader literature base. [For the complete proceedings, see ED630210.]