Critical-thinking development can enhance students' reasoning and thinking abilities, but the extent to which additional critical-thinking instruction can enhance academic performance remains unclear. Therefore, there is a need to investigate whether providing additional critical-thinking instruction can improve academic performance. This study examined the impact of additional mathematics interventions on the academic performance of fourth-grade students, with a focus on enhancing critical-thinking skills. Specifically, the study aimed to determine if a significant difference existed in academic performance between students who received additional mathematics instruction and those who did not at a K-5 public charter elementary school in Florida. The study also explored whether gender moderated this difference. Using a quantitative, quasi-experimental approach, the study collected and analyzed data on academic performance from both groups of students. The study found a statistically significant difference between the academic performance of students who received additional mathematics interventions compared to students who did not. The results of this study have several implications for future research and practice. The presented study offers implications for future research, policy, and professional practice in the field of critical-thinking achievement in mathematics education. The study highlights the positive relationship between critical-thinking instruction and mathematics proficiency and suggests that further research is necessary to clarify this link and to identify effective teaching methods that prioritize critical-thinking skills. The findings of the study may encourage the inclusion of critical-thinking strategies in math curriculum and provide insights for the development of teaching resources or programs for instructor professional growth. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]