With the passage of the No Child Left Behind Act of 2001, public school districts in the United States are working toward improving the achievement of their students on state standardized tests of accountability. Through the use of a quantitative methodological approach, the purpose of this study was to better understand the relationship, if any, between secondary mathematics teachers' use of teacher-created common assessments in the classroom and students' achievement on state accountability tests in mathematics. Based within the theoretical context of the importance of professional development and collaboration of teachers in improving student achievement, this study answered the following research question: Will the achievement of 11th-grade students on a state's accountability test in mathematics, the grade 11 Mathematics Minnesota Comprehensive Assessment Series test, vary with the exposure to the strategy of teacher-created common assessments during instruction prior to taking the grade 11 Mathematics MCA? This study was interested in high school students, and the convenience sample consisted of approximately 2,760 11th-grade mathematics students' scores from years 2006-2011. Each student within the selected sample completed an 11th-grade mathematics course prior to taking the grade 11 Mathematics MCA. After an analysis of the data collected by use of the grade 11 Mathematics MCA, this study proved the following hypothesis: The use of teacher-created common assessments impacts high school students' achievement in mathematics. [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.]