A Rasch Model approach to measuring school need for psychological services

Year: 2009

Author: Young, Adrian, Cavanagh, Rob

Type of paper: Refereed paper

The role and deployment of school psychologists in Western Australia has been reviewed a number of times since the establishment of services to schools. Current practices whereby school psychologist allocation to schools is achieved continues to appears to rely on school student population figures, its socioeconomic index and an appraisal of the school’s “difficulty” level. Psychological services are then allocated accordingly, the decision-making mechanism based on an ad hoc conception of school need.

The research reported in this paper concentrated on the issue of trying to establish what aspects or characteristics of schools constitutes a greater or lesser level of need for services and then attempt to measure this need in an objective evidence-based manner. The various elements of school need for psychological services are posited to cluster around constructs extrapolated from the domains of service reported in the international professional literature. These are characteristics of students, characteristics of schools and teacher expertise. The three constructs constitute the preliminary conceptual framework for the study upon which the empirical investigation was based.

The study was conducted in three phases: First, theoretical framework refinement utilising data collected from a questionnaire; second item development, piloting and trialling; and third, utilising a refined linear scale to measure a sample of schools need for psychological services. Data were obtained from samples of principals, teachers and school psychologists working in two Department of Education and Training (DET) school districts. Data analysis employed the Rasch Rating Scale Model and Analyses of Variance. Data fitting the model confirmed that a uni-dimensional trait was measured. Data-to-model fit was estimated by item difficulty thresholds, individual item fit statistics, the person Separation Index and Principal Components Factors loadings of residuals. The results demonstrated that the linear scale instrument developed in the research provided an authentic measure of school need and that the measures of the phase three schools differed significantly from each other. The empirical findings of the study are discussed in the context of their application in informing decisions about the level of psychological services that should be provided to schools congruent with the psychological needs of their students.