We examine pre-service teachers’ theoretical learning during one five-week training module, and their educators’ learning about better lecture design to foster student learning. The study is iterative: interventions (one per group) were implemented sequentially in student groups A–C, the results of the previous intervention serving as the baseline for the design developed for the next. These learning study participants, 79 students from year three of a teacher training programme, studied the variation theory (VT) of learning. Three lesson cycles were completed, each comprising four steps: (1) a pre-test, (2) a 15-min intervention discussing VT, (3) a post-test and (4) a delayed post-test conducted eight weeks later. The results indicated learning differences between groups; qualitative analysis identified three categories of student answers, i.e. emergent, premature and unaware, regarding their theoretical understanding. Group C had more students with emergent knowledge (36%) than did groups A (20%) or B (17%) at post-testing.