A change in our measure of teaching style can be interpreted as a shift from spending time on one practice to spending time on the other, holding constant the total time spent on both practices. For example, an increase of 0.1 indicates that 10 percentage points of total time devoted to teaching new material are shifted from teaching based on problem solving to giving lecture-style presentations. We combined the other teaching activities (besides lecturing and problem solving) into a separate measure of the share of total teaching time devoted to other activities and control for this measure throughout our analysis. We also control for the total number of minutes per week that the teacher reported teaching the math or science class, as more total instructional time could have an independent effect on student learning.