Teacher grading practices commonly do not align with the grading practices recommended by leading grading authorities in the field of education. The experts advocate for grades to be determined solely from measures of product criteria that represent a students current level of knowledge and what they can do. Most teachers, however, still use a mix of process, progress and product criteria that combine the students work habits, behaviors and how much progress they have attained with what they know and can do in the determination of a students aggregated grade. This mixed methods study focused on whether or not the grading practice of incorporation of process criteria into students summative grades affected student achievement in high school mathematics and English courses as measured by criterion reference test scores. In addition, this study compared teacher grading practices and actual course grades to students achievement as measured by the course criterion reference test score to determine if the relationship between achievement and semester grades was effected by teacher grading practices. Qualitatively, this study analyzed teacher practices and their perceptions and knowledge of best practices with regards to common grading practices. Data for the study was collected from a Chicago, south suburban mid-sized four high school district with a population of slightly over five thousand students. For the quantitative part of the study, the sample was randomized from a population of students whose math and English teachers participated in a survey with respect to their individual grading practices. The qualitative data piece was collected from a convenience sample of teacher surveys and individual interviews. [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.]