The purpose of this quantitative, comparative study was to examine if and to what extent, there are statistically significant differences in decoding and oral reading fluency scores between at-risk Title I students who receive multisensory phonics-based instruction in first grade and those who do not in the Western United States. Paivio's dual coding theory underpins multisensory instruction through reading content. The four research questions asked whether statistically significant differences in decoding and fluency existed in Tier 2 and Tier 3, between Title I first-grade students who received multisensory phonics-based instruction and students who did not participate in reading instruction, as measured by the aimsWeb Plus assessment. The sample included only 43 students in Tier 2 and 193 in Tier 3. Statistical tests were performed only on the Tier 3 sample that included 91 students who took traditional instruction and 102 students who took multisensory instruction. The results on nonparametric Mann-Whitney U tests showed statistically nonsignificant differences between the Tier 3 traditional and the multisensory groups in terms of decoding (U = 4343, W = 9596, std. U = -0.774, asymptotic sig. = 0.439, d = 0.118) and in terms of fluency (U = 5165.5, W = 10418.5, std. U = 1.363, asymptotic sig. = 0.173, d = 0.284). The distributions of decoding and fluency scores in Tier 3 were non-normal and showed spikes for zero values. These nonsignificant results are inconclusive. As more districts adopt multisensory phonics-based instruction programs to prevent reading failure among first graders, more research is needed to assess the effectiveness of such programs for Tier 2 and Tier 3 at-risk 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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]