The Social Cognitive Theory (SCT) is a widely used theory for nutrition education programming. Better understanding the relationships between knowledge, self-efficacy, and behavior among children of various income levels can help to form and improve nutrition programs, particularly for socioeconomically disadvantaged youth. The purpose of this study was to determine the relationships between knowledge, self-efficacy, and behavior among fifth grade students attending Title I (≥40% of students receiving free or reduced school meals) and non-Title I schools (<40% of students receiving free or reduced school meals). A validated survey was completed by 55 fifth grade students from Title I and 122 from non-Title I schools. Differences in knowledge, self-efficacy, and behavior scores between groups were assessed using t test and adjusted for variations between participating schools. Regression analysis was used to determine the relationships between knowledge, self-efficacy, and behavior. In adjusted models, the Title I group had significantly lower scores on several knowledge items and summary knowledge (P = 0.04). The Title I group had significantly lower scores on several behavior variables including intakes of fruits (P = 0.02), vegetables (P = 0.0005), whole grains (P = 0.0003), and lean protein (P = 0.047), physical activity (P = 0.002) and summary behavior (P = 0.001). However the Title I group scored higher on self-efficacy for meal planning (P = 0.04) and choosing healthy snacks (P = 0.036). Both self-efficacy (β = 0.70, P < 0.0001) and knowledge (β = 0.35, P = 0.002) strongly predicted behavior; however, only self-efficacy remained significant in the Title I group (self-efficacy, β = 0.82, P = 0.0003; knowledge, β = 0.11, P = 0.59). Results demonstrate disparities in nutrition knowledge and behavior outcomes between students surveyed from Title I and non-Title I schools, suggesting more resources may be necessary for lower income populations. Findings suggest that future nutrition interventions should focus on facilitating the improvement of children's self-efficacy.