On assessments such as Trends in International Mathematics and Science Study (TIMSS) (Stigler & Hiebert, 1999) and Program for International Assessment (PISA) ("PISA 2006 Science Competencies for Tomorrow's World", 2007) students in the United States have not been performing as well in mathematics as students in other countries. In order for the United States to remain a global leader, it is important to look to find ways to increase our students' mathematical achievement. This dissertation examined how music education in four suburban New Jersey schools may be related to learning mathematics. It presents a detailed description of a study that investigated the correlation between student achievement on the mathematics section of the New Jersey High School Proficiency Assessment (HSPA) and the amount of formal musical training they had experienced. The study considered student achievement on each of the four mathematics clusters (sub-sections) as well as the overall mathematics assessment. This study used a combination of quantitative and qualitative data to answer the research questions. Mathematics is one of the topics assessed by most high-stakes tests. As a result, many schools have increased the amount of time devoted to studying mathematics. However, many schools have decreased their emphasis on the arts, including music, in their curriculum (Lehman, 1993; VH1 Save the Music Foundation, 2006). The study sample consisted of 47 high school students who have taken the NJ High School Proficiency Assessment previously in March of their junior year. For this study, three types of data were collected; participants completed a survey, their total scaled HSPA test score and four cluster scores were obtained, and an interview was conducted with a small number of participants. There was a significant difference between the total scaled HSPA score and three of the four cluster scores for musicians and non-musicians. When the score for the lone low scoring musician outlier was removed from that cluster, the difference was also significant. There was little to no correlation between the number of years studied and HSPA scores and time since last music lesson and HSPA scores, little to no correlations between the number of music courses taken in grades nine through eleven and HSPA scores, and there was not a significant difference between one's primary instrument and HSPA scores. [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.