Background: Research demonstrates a link between decreased cognitive function in overweight school-aged children and improved cognitive function among students with high fitness levels and children engaging in regular physical activity (PA). The purpose of this study was to examine whether regular PA and proper nutrition together had a significant effect on academic achievement. Methods: Using the seventh wave of the Early Childhood Longitudinal Study, Kindergarten Class 1998-99 (ECLS-K) dataset, linear regression analysis with a Jackknife resampling correction was conducted to analyze the relationship among nutrition, PA, and academic achievement, while controlling for socioeconomic status, age, and sex. A nonactive, unhealthy nutrition group and a physically active, healthy nutrition group were compared on standardized tests of academic achievement. Results: Findings indicated that PA levels and proper nutrition significantly predicted achievement scores. Thus, the active, healthy nutrition group scored higher on reading, math, and science standardized achievement tests scores. Conclusions: There is a strong connection between healthy nutrition and adequate PA, and the average performance within the population. Thus, results from this study suggest a supporting relationship between students' health and academic achievement. Findings also provide implications for school and district policy changes.