This quantitative study evaluated how two consecutive years of math Response to Intervention (RtI) demonstrated its effectiveness on 995 fifth grade students within the School District A (SDA) on Smarter Balanced (SB) assessments. Research questions: "What is the relationship between the duration of math RtI implementation and math performance as measured by DCAS and SB?" "What is the relationship between DCAS and SB in math performance?" An ex post facto experimental design was utilized on archived Delaware Comprehensive Assessment System (DCAS) math scores and SB math scores with SDA data. To answer research question one, the one-way repeated measures ANOVA was utilized and its result supported a decision to conclude that there was a higher level of significant improvement in math scores after RtI. A total sample analysis indicated significance (p < 0.05). The individual school building analysis indicated significance (p < 0.05) with the exception being among four school buildings. To answer research question two, a Correlational Analysis was utilized and its result indicated strong positive correlations, p < 01. The finding indicated that the two instruments, DCAS and SB, measured the same math standards similarly, meaning that the measurements of math performance were comparable, and SB was an appropriate math assessment replacement for DCAS. These results suggest that in the first year of RtI implementation, there was a large increase in students' math scores as measured by SB 2015 but with continued implementation of RtI for a second year, there was minimal significant growth from 2015 as evidenced by SB 2016. This minimal growth from 2015 to 2016 may suggest that students reached a peak level of performance after math RtI administration, may have reached a maximum threshold in math performance and may benefit further with additional teaching supports or strategies to continue to increase their math performance. [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.]