Current research shows that, despite standards-based mathematics reform, American students lag behind in mathematics achievement when compared to their counterparts in other countries. The purpose of this mixed methods study was to examine if reading level, as measured by the Scholastic Reading Inventory, is related to standards-based mathematics achievement, as measured by the Georgia Criterion Referenced Competency Test (CRCT). An information processing theory of language acquisition was used to frame the study. Pearson product-moment coefficient correlation tests were run to examine if a relationship exists between Lexile levels and GCRCT scores. The perceptions of 6th grade mathematics teachers regarding this relationship were also explored using open ended, qualitative interview techniques. Results of the quantitative data analysis showed moderate positive relationships between reading level and all subdomains of standards-based mathematics achievement. Qualitative data revealed that 6th grade mathematics teachers identified reading ability as a contributing factor to standards-based mathematics achievement. Recommendations for further study include assessing general intelligence and working memory as additional factors that may contribute to standards-based mathematics achievement. This study has potential to affect social change by identifying ways in which reading level can be used to improve mathematics achievement among American students. The success of American students is important to both the students and their schools, and their future performance is important to everyone, as these students will globally compete for Science Technology Engineering and Mathematics jobs on behalf of America. [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.]