This study examined the impact of curricular factors and teaching practices on students' tested achievement in mathematics, explored the best predictors of the tested achievement, and examined differences in the tested achievement among student subgroups. The study utilized qualitative and quantitative methods and triangulated findings from teacher surveys, observations, teacher syllabi, and curriculum scales. The study found that there were differences in tested achievement in high school mathematics among student subgroups and that the best predictors of differential achievement in math were academic track, GPA and school coursework factors. Students in different schools and tracks were found to have differential access to rigorous curricula and qualified teachers. In general, students who had access to more rigorous courses and teachers and whose schools showed higher curriculum quality performed better on state assessments. [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.]