Background: Approximately 20% of US children are obese and these rates are expected to increase. The National School Lunch Program (NSLP) provides meals to millions of students and may influence their body mass index (BMI). This study aimed to investigate whether students who participate in the NSLP have a higher BMI when compared to those that do not. Methods: Secondary data from the US Census Bureau were analyzed. Kruskal-Wallis H tests were performed to find associations between NSLP participation and students' BMI. Race and economic stability were included as moderating variables. Results: NSLP participation and respondents that identified as White/Caucasian, African American, and Native American were positively associated with BMI. Lower economic stability was also positively associated with BMI. Conclusion: Participation in the NSLP was significantly associated with participants' BMI, race, and economic stability. While a cause-and-effect relationship cannot be determined, these results are important given their potential influence on students' long-term health.