This technical report presents results from a cross-validation study designed to identify optimal cut scores when using easyCBM[R] reading tests in Washington state. The cross-validation study analyzes data from the 2009-2010 academic year for easyCBM[R] reading measures. A sample of approximately 900 students per grade, randomly split into two groups of roughly the same size, was used for this study. Students state test performance classification (passing/not passing) on the Measurements of Student Progress (MSP) state test in Washington was used as the criterion. Optimal cut scores were identified for each of the randomly split groups with a receiver operating characteristic curve (ROC) analysis. Results indicated reasonably stable cut scores between groups. Further, the overall area under the ROC curve (AUC) was not statistically different between groups for any measurement occasion at any grade, providing strong evidence for the validity of identified cut scores as optimal to predict student performance classification on the Washington state large-scale assessment.