Some schools have adopted homogenous grouping of students for academic instruction in response to the No Child Left Behind Act, which requires school districts to ensure academic achievement for all students. The early intervention program (EIP) in mathematics is provided for below-grade level students, yet many of them continue to perform poorly after they receive assistance. The purpose of this ex post facto descriptive quantitative study was to investigate the effectiveness of the EIP on the mathematics achievement of students in 4th grade as compared with the mathematics achievement of non-EIP 4th grade students over 4 consecutive academic years. The grouping/tracking theory served as the theoretical framework for this study. The guiding questions for the study investigated the impact of EIP on the math achievement scores of 4th grade EIP students. Archival data were collected from the Criterion-Referenced Competency Tests for 2007-2008, 2008-2009, 2009-2010 and 2010-2011. Data were analyzed using frequency distributions, descriptive statistics, and a two-way ANOVA. Results of the ANOVA showed that the performance of the EIP group remained substantially lower than the performance of the non-EIP group. Findings also indicated that the achievement gap between EIP and non-EIP students did not change over 4 years. Further investigation into differentiated instructional practices is needed to ensure that all students are successful in mathematics. It is recommended that school administration provide professional development for EIP teachers that can result in improved standardized math scores. Implications for social change include providing EIP teachers research-based mathematics strategies to close the academic gap between EIP and non-EIP students. [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.]