Fig. 1

Study Design with randomization to the three conditions in two steps

In the first step (Spring 2023), 16 high schools were recruited and randomized to a control (5 control high schools) or intervention (11 intervention high schools) condition. In the next step (November 2023), randomization occurs at class-level within the intervention schools, i.e., half of the classes at the 11 intervention schools are randomized to the structural only condition and the other half are randomized to the structural + group MI condition