This study investigates the influence of Explicit Instruction (EI) on the mathematics achievement of students attending Belmont Middle School (BMS). There is an urgent need for schools to evaluate the instructional strategies they have been adopting to identify whether they have any significant impact on students' mathematics performance. With the adoption of EI at BMS after years of below-average mathematics proficiency rankings across the state, it is imperative to analyze how EI impacts students' mathematics proficiency levels. Therefore, the study aimed to assess the effectiveness of EI in improvements in mathematics proficiency, using both quantitative and qualitative methods to offer a comprehensive understanding. Standardized test scores were used to gather quantitative data, while teacher interviews provided qualitative insights. The paired samples' t-tests through SPSS indicated a lack of statistical significance (p=0.074), though quite close to the alpha 0.05, suggesting a possible trend toward significance with time. The correlations between the duration of EI implementation and students' mathematics performance were strong at r=0.891, suggesting positive effects of consistent EI practices on student math achievement. The qualitative results illuminated key themes such as teacher confidence level in employing EI strategies and observed improvements in mathematics proficiency. Actionable recommendations are proposed for educators and policymakers through a detailed action plan that BMS should implement. [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.]