This quantitative method, quasi-experimental design study examined the possible effect of foreign language study in Tennessee middle schools on mathematics achievement. The population was 1,708 historical student test scores of a single cohort spanning 6th through 8th Grades from the same schools within a large urban public school district. NCLB demographics included race, gender, socio-economic status, and ELL status. The quasi-experimental design followed methods described by Shadish, Cook, & Campbell, including independent control and treatment groups, pre-test/post-test, stratification, and matching. The instrument was the mathematics portion of the revised (2008-2009) Tennessee Comprehensive Assessment Program (TCAP) standardized tests. The TCAP was revised with increased critical thinking skills according to the Webb taxonomy and normalized to national standards. The study indicated that the foreign language treatment group performed significantly better than the control group, t[subscript 2-samp] (8) = 4.87, a <0.05, on their 8th Grade TCAP mathematics test. The problem was that foreign language programs had been reduced or eliminated under NCLB-related academic and financial pressures. Political and educational leadership lacked evidence linking foreign language study to mathematics achievement in middle schools. This study was situated within an intuitionist mathematics philosophy, brain-based research, and social cognitive learning theory. Implications included an age-appropriate curriculum development model, curricular integration, support for foreign language study in middle schools, and the possible detrimental effects of cancelling foreign language programs. [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.]