Measuring Professional Competency in School Counselors: Development and Rasch Validation of a Multidimensional Instrument

Background The measurement of professional competency in school counseling remains methodologically constrained by fragmented domain assessment and heavy reliance on classical test theory approaches. There is a critical need for an empirically calibrated instrument that integrates regulatory competency standards with expanded theoretical domains while ensuring measurement precision and structural coherence. This study developed and validated a multidimensional instrument of professional competency for school counselors using Rasch analysis. Methods A cross-sectional instrumental design was implemented. The instrument was constructed across seven domains: assessment, development of guidance and counseling program, implementation of guidance and counseling services, evaluation of guidance and counseling program, supervision of pre-service counselor training, continuous professional development, and collaborative engagement in co-curricular programs. Seventy-one items were rated on a five-point Likert scale. Data from 93 practicing school counselors were analyzed using the Rasch Rating Scale Model. Analyses included the evaluation of category functioning, item and person fit statistics, reliability and separation indices, and principal component analysis of residuals (PCAR) to assess construct dimensionality. Results The Rasch model demonstrated acceptable item fit and ordered rating scale thresholds. The raw variance explained by measures was 53.4%, with 6.7% unexplained variance in the first contrast, indicating a dominant latent construct despite the multidomain theoretical structure. Item difficulty estimates ranged from −1.68 to +1.71 logits, forming a hierarchical continuum from foundational service practices to advanced supervisory and professional roles. Reliability and separation indices indicated stable item calibration and adequate differentiation among levels of professional competency. Conclusions The findings support the structural validity, hierarchical calibration, and measurement precision of the instrument within a unified Rasch framework. The instrument provides a methodologically robust basis for professional assessment, supervision, and competency-based development in school counseling contexts, with significant potential for further validation across diverse educational systems.