Background: While mask mandates are unlikely to return in the event of a major resurgence in COVID-19 or another major respiratory disease surge, voluntary masking still shows promise. This ethnographic study seeks to understand the masking decision-making processes of parents and children in the diverse San Diego region, including US-Mexico Border school districts and military housing school communities. Methods: We conducted 19 interviews with parents and their young children focused on COVID-19 efforts at their child's school in English and Spanish and collected detailed field notes on masking culture from over 60 systematic observations from elementary schools across San Diego County from December 2021 to May 2022. We conducted analysis using Dedoose, including multiple rounds of coding and ongoing consensus meetings between researchers. Results: Guided by the social ecological model (SEM), we categorized the results into the following categories: Children's Attitudes and Behaviors, Parent Belief and Influence, School Culture, and District/School Mask Mandates. Each level of the SEM influenced individual and family masking behavior. In our data, School Culture in particular differentiated schools in mask adherence and encouraged masking after state mandates ended. Implications for School Health Policy, Practice and Equity: Masking does not need to end with mandates. Masking has been proven to reduce COVID-19 transmission, and school health policies should consider encouraging masking beyond mandates. Conclusions: Adapting health messaging to the local context, partnering with trusted community champions, and building trust across governmental, school, and public health entities can improve the effectiveness of public health messaging.