Background: The association of physical fitness with cognitive function in children and adolescents is unclear. The purpose of this ecological study was to describe the association between academic achievement, body mass index (BMI), and cardiovascular fitness (CVF) in a large sample of elementary, middle, and high school students in Texas. Methods: FITNESSGRAM® results for 2,550,144 students were matched with standardized composite academic test (TAKS) results from 2008 to 2009. Analyses were conducted on the percent of students meeting TAKS standards by BMI and CVF quintiles. Analyses of variance with Tukey adjustment examined differences between the most favorable 5th quintile (referent) and all other quintiles. Results: The prevalence of students meeting the TAKS standard was significantly higher in the highest fitness category for BMI and CVF compared to all other categories, regardless of sex or grade category (p?< 0.05). Linear modeling suggested a 5% increase in the prevalence of students meeting healthy BMI and CVF standards would result in a 2.25% and 0.65% increase in the prevalence of students meeting the TAKS standard (both p?< 0.05). Conclusion: Findings suggest a healthy BMI and CVF are associated with higher academic achievement, and the need for additional research examining the role of potential confounders and/or effect modifiers longitudinally.