Background: Current evidence demonstrates that, while a widely-used tool for childhood obesity prevention, school-based body mass index (BMI) reports do not effectively reduce pediatric obesity. The purpose of this study was to examine the presumed mechanisms by which BMI reporting might impact child weight by assessing parents': 1) recall of BMI reports, 2) accuracy in recalling child overweight status; and 3) reactions to BMI reports. Methods: Mailed surveys were completed by 2,205 racially/ethnically diverse parents of 3rd-7th grade students participating in the Fit Study who had either been exposed to 1 year of child BMI reporting (1 report) or 2 years (2 reports). Results: After 1 year of BMI reporting, parents of children with overweight were less likely (OR=0.7, 95% CI: 0.5, 0.9) to recall receiving a BMI report and less likely (OR=0.2, 95% CI: 0.1, 0.3) to accurately recall their child's weight status from the BMI report, compared to parents of children with healthy weight. Differences in accuracy of child weight-status recall persisted after 2 years of BMI reporting exposure. Only 22% of parents of children at risk for overweight and with overweight reported being surprised by the results. Conclusions: Parents' recall of receiving a school-based BMI report is low, as is the accuracy of recall of child's overweight status. Additionally, parents' surprise at, and concern for, BMI results is limited. Current BMI reports may be ineffective at reducing pediatric obesity due to their lack of salience and ability to compel meaningful behavior change among parents.