Each spring, Arizona students participate in testing as part of the state's assessment program. Elementary and middle school students in grades 3 through 8 take the Arizona Instrument to Measure Standards--Dual Purpose Assessment (AIMS DPA) in reading, writing, and mathematics. These tests serve as an important measure of student achievement for the state's accountability system. Results from these assessments are used to make state-level decisions concerning education, to meet "Adequate Yearly Progress" (AYP) reporting requirements of the "No Child Left Behind Act" (NCLB), calculate status and improvement indicators for AZ LEARNS, the state accountability system, and to inform schools and school districts of their performance. The Arizona Department of Education has developed scales that are used to assign students to one of four performance levels on these tests. Many students who attend school in Arizona also take tests developed in cooperation with the Northwest Evaluation Association (NWEA). The content of these tests are aligned with the Arizona standards and they report student performance on a single, cross-grade scale, which NWEA calls the RIT scale. This study investigated the relationship between the scales used for the AIMS assessments and the RIT scales used to report performance on Northwest Evaluation Association tests. The study estimated the changes in reading and mathematics RIT score equivalents for the AIMS performance levels in those subjects. Test records for more than 20,000 students were included in this study. The information gathered in this study came from measures employing the NWEA RIT Scale. Because all of the research that we have to date indicates that scores generated from computer-based tests and Achievement Level Test (ALT) scores are virtually interchangeable, readers should feel comfortable applying the results of this study in any setting that uses the RIT scale. (Contains 14 tables and 6 figures.)