This quantitative study explored the academic progress of at-risk students in English language arts (ELA) when they were given differentiated instruction (DI) and universally designed curriculum (UDC) to address their academic needs. The purpose of the study was to determine if there was a significant change in passing rates on the California Standards Test (CST) for at-risk students instructed with DI and UDC when compared to the scores of at-risk students who were instructed with a standardized core curriculum. The study utilized archival data from the California Standards Testing and Reporting website to collect data. The population included students in 4th, 5th, and 6th grades who were identified as at-risk students in the area of ELA due to test scores of Far Below Basic and Below Basic on the CST. The study was conducted with students in a rural school district in Southern California. The results of the data analysis demonstrated the effects of DI and UDC when compared to the standardized core curriculum on student test scores during the 2007-2008, 2008-2009, 2009-2010, and 2010-2011 school years. The findings from the study may assist districts in choosing the appropriate curriculum to address the needs of at-risk learners. Based on the results derived from data analysis that utilized t tests and z tests, it was concluded that when comparing test scores at the same grade level over the years included in the study, those with DI/UDC outperformed those with the standardized core curriculum. However, when comparing grades with DI/UDC, no significant differences were found. Educational researchers should continue to assess the relationships between DI/UDC and the resulting passing rates of at-risk students participating in state assessments. [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.]