Inside the BASC-3 TRS: What Multidimensional IRT Reveals

This study presents a multidimensional item response theory analysis of the Behavior Assessment System for Children, Third Edition, Teacher Rating Scales (BASC-3 TRS). Using item-level data from 563 teacher ratings of referred students, we evaluated the dimensional structure, item functioning, and measurement precision of the Externalizing Problems, Internalizing Problems, School Problems, Behavioral Symptoms, and Adaptive Skills composites and their subscales. Correlated-factor, higher-order, and bifactor graded response models were compared, with bifactor models providing the best overall fit across domains. General factors accounted for substantial proportions of reliable variance, although the degree of subscale specificity varied. Several subscales, including Adaptability, Social Skills, Hyperactivity, Somatization, Withdrawal, and Learning Problems, retained meaningful domain-specific variance, whereas others were largely saturated by their respective general factors. Item-level results indicated well-ordered thresholds, strong discrimination, and high measurement precision in clinically relevant regions of the latent traits. These findings clarify the structure of the BASC-3 TRS, provide evidence supporting the composite scores as defensible indicators of broad behavioral and emotional functioning, and identify the subscales for which the psychometric evidence most strongly supports meaningful and interpretable score use.