Importance: Screening and brief intervention (SBI) programs in schools have the potential to provide substance use prevention messages to large numbers of adolescents. This study evaluated the association between exposure to a school-based SBI program and reductions in substance use among youths after enactment of a law that required Massachusetts schools to provide SBI to all students.

Question: Is exposure to a screening and brief intervention (SBI) program in schools associated with reductions in student substance use?

Findings: In this quality improvement study involving 4587 students in grades 7 through 10 who were exposed to a school-based SBI program in Massachusetts, cannabis and e-cigarette use increased over time in all groups. Exposure to SBI was associated with a significantly smaller increase in the rate of cannabis use among middle school students and significantly smaller increases in the rates of cannabis and e-cigarette use among all female students; however, there was no significant difference in any comparison among all high school students.

Meaning: This study’s findings suggest that school-based SBI programs, which are mandatory in Massachusetts, may help to reduce substance use among middle school and female students.