Key PointsQuestionHow can reporting of racial and ethnic representativeness in pediatric research studies be optimized for specificity and replication to address methodological gaps and reduce health disparities?FindingsIn this cross-sectional study with a pooled sample of 104 schools located in 5 US states, the Bland-Altman method was adapted to quantify school-level racial and ethnic representativeness using measures of spread. Overall representativeness was observed, yet group means obscured the substantial within-group disparities observed with residuals on Bland-Altman plots.MeaningThese results suggest that replication of the proposed Bland-Altman method may improve race and ethnicity reporting, representative recruitment, and external validity of the health evidence base.