This quantitative correlational study was designed to determine if and to what extent there was a relationship between the Arizona Assessment Collaborative (AZAC) district benchmark assessment scores and the Arizona's Measurement of Educational Readiness to Inform Teaching (AzMERIT) state achievement test scores for reading and math for students with disabilities in grades three through eight. The sample used in this study was 526 paired observations that included a score for the AZAC and AzMERIT in math and reading. The students with special needs whose scores were included in the study attend a 15 school district in Arizona. This study was based on the formative assessment theory and was intended to add to the body of knowledge surrounding the assessment and instruction of students with special needs. Research questions that guided this study asked whether there was a relationship between the two sets of scores for the students in grades three through eight. Preliminary analysis of the variables showed the data to be approximately normally distributed, to be linear, and not have any outliers, thereby meeting the assumptions of the Pearson correlation. A Pearson test was run indicating a positive correlation between these two sets of scores, r[subscript s] (526) = 0.337, p < 0.0005 for math and r[subscript s] (526) = 0.351, p < 0.0005 for reading. The null hypotheses were rejected, and the alternative hypotheses were accepted. This positive correlation between these two sets of scores will impact future educational decisions regarding instruction and assessment of students with special needs. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]