This study investigated the effects of using modified items in achievement tests to enhance accessibility. An experiment determined whether tests composed of modified items would reduce the performance gap between students eligible for an alternate assessment based on modified achievement standards (AA-MAS) and students not eligible, and the impact on student proficiency levels. Three groups of eighth-grade students ( N = 755) from four states took original and modified versions of reading and mathematics tests. Findings indicate modified item conditions were significantly easier for all students and modifications would result in more AA-MAS eligible students meeting proficiency status. Study limitations and follow-up research on item modifications and the performance of students with disabilities are discussed.