"Parents play an important role in shaping the decisions their children make when it comes to alcohol and marijuana," says Dr. Toby Parcel, a professor of sociology at NC State and co-author of a paper on the work. "To be clear, school programs that address alcohol and marijuana use are definitely valuable, but the bonds parents form with their children are more important. Ideally, we can have both."

The researchers evaluated data from a nationally representative study that collected information from more than 10,000 students, as well as their parents, teachers and school administrators.

Specifically, the researchers looked at how "family social capital" and "school social capital" affected the likelihood and/or frequency of marijuana use and alcohol use by children. Family social capital can essentially be described as the bonds between parents and children, such as trust, open lines of communication and active engagement in a child's life. School social capital captures a school's ability to serve as a positive environment for learning, including measures such as student involvement in extracurricular activities, teacher morale and the ability of teachers to address the needs of individual students.

The researchers evaluated marijuana use and alcohol use separately. In both cases, researchers found that students with high levels of family social capital and low levels of school social capital were less likely to have used marijuana or alcohol -- or to have used those substances less frequently -- than students with high levels of school social capital but low family social capital.