There is compelling empirical evidence in support of the use of grouped self-assessment data to measure program outcomes. However, other credible research has clearly shown that self-assessments are poor predictors of individual achievement such that the validity of self-assessments has been called into question. Based on the reanalysis of two previously published studies and an analysis of two original studies, we show that grouped self-assessments may be good predictors of and hence valid measures of performance at the group level, an outcome commonly used in program evaluation studies. We found statistically significant correlation coefficients (between 0.56 and 0.87), when comparing across performance items using the group means of self-assessments with the group means of individual achievement on criterion tests. We call for further research into the conditions and circumstances in which grouped self-assessments are used, so that they can be employed more effectively and confidently by program evaluators, decision makers, and researchers.