The Virginia public-school assessment and accountability system impacted the statewide reading proficiency scores for students with disabilities. The purpose of this causal-comparative quantitative study was applied to answer the research question, and hypothesis statement and determine the difference in the reading improvement measured by the NWEA MAP Growth Testing RIT scores for students with disabilities (SWD) with the support and non-support of the Wilson Reading System (WRS) direct instruction in Virginia public middle schools for two consecutive years. This causal-comparative study was important for school divisions that used intervention strategies as a support for students reading below grade level. The Wilson Reading System was an intervention strategy applied for SWD to see if there was a difference in the reading improvement measured by the NWEA MAP Growth Testing RIT scores in direct instruction. During the years 2018-2019 and 2019-2020, the sample size comprised a total of 840 SWDs with a selected 105 students supported and 105 not supported with the WRS established by the G-Power statistical power analyses tool. Statistical analysis was implemented by the Statistical Package for the Social Sciences (SPSS). An independent samples t-test was conducted to analyze the MAPS scores indicating a significant difference for SWDs supported by the Wilson Reading System program compared to the SWDs that the WRS did not support. This study may be used by practitioners and leadership to make decisions on the approval of direct instructional models beneficial to students with low proficiency performances. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]