Researchers investigated the diagnostic utility of the Social Skills Improvement System: Performance Screening Guide (SSIS-PSG). Correlational, regression, receiver operating characteristic (ROC), and conditional probability analyses were run to compare ratings on the SSIS-PSG subscales of Prosocial Behavior, Reading Skills, and Math Skills, to report card grades for conduct, reading, and math, respectively. Respective subscales were all statistically significantly correlated with one another. In addition, all regressions indicated significant predictions for the SSIS-PSG to respective report card grades. ROC analyses for SSIS-PSG Math with math grades and SSIS-PSG Reading with reading grades were statistically significant and described as fair. ROC analysis for SSIS-PSG Prosocial Behavior with conduct grades was not significant and described as poor. In a conditional probability analysis, the variable of concern for screeners concerns false negative ratios; all estimates for this fell within the targeted range.