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.