Procedure
Each parent or caregiver and student independently completed a baseline survey in spring of students’ senior year in high school. Then, early in the summer, we sent copies of the handbook to parents in the intervention conditions. As an implementation strategy, we hired graduate student research assistants to increase parent engagement by calling intervention parents to encourage them to read the handbook and complete the activities. To facilitate conversations with parents about using the handbook, research assistants received 8 h of training on a standardized call protocol from one of the investigators and one of the PIs approximately 1 month before the handbooks were mailed to families. The training provided information about the handbook, motivational interviewing skills, and opportunities to practice using motivational interviewing. After completing at least three practice calls with the research team and being approved by the senior family outreach supervisor, each research assistant was assigned an average of 48 families. Once handbooks had been sent, research assistants began calls to parents in the intervention condition and successfully contacted 76% (