Background: Most pediatric elevated blood pressure (BP) remains undiagnosed. The American Academy of Pediatrics states "there is limited evidence to support school-based measurement of children's BP." We explored the utility school-based BP screening. Methods: A cross-sectional sample of 4096 students ages 6 to 17 from Title 1 Miami-Dade Public Schools (50% female, 71% non-Hispanic black, 26% Hispanic) had their systolic/diastolic BP (SBP/DBP) and body mass index (BMI) collected over the 2016 to 2017 or 2017 to 2018 school years. Relative risks (RRs) ratios were calculated to estimate normal/elevated SBP/DBP by BMI percentile, ethnicity, and sex. Results: Overall, 26.4% had at least one elevated BP measurement, of which 59% were not obese. RR for obese status was significant for all categories of elevated BP (RRs > 1.88, p < 0.0001). Being either female (RR = 1.34, p = 0.009) or Hispanic (RR = 1.31, p = 0.014) was significantly associated with elevated DBP. BMI accounted for <10% of the variation in BP (SBP: F(1, 4095) = 367.6, adjusted R[superscript 2] = 0.08, p < 0.0001; DBP: F(1, 4095) = 93.3, adjusted R[superscript 2] = 0.02, p < 0.0001). Conclusion: These findings support providing BP screenings in school settings. Low-income and minority students often have limited access to health care, higher obesity rates, and unhealthy behaviors. Our findings support universal school-based BP screening regardless of weight status, particularly among ethnically diverse populations.