The problem addressed in this study was that some high school students do not have the math skills needed to succeed in a traditional chemistry class. If instructional strategies are not changed, many students who struggle with algebra will also struggle to master the chemistry content which is a required high school subject in Arizona. The purpose of this qualitative action research study was to explore teachers' perspectives and students' performance to determine if and how modeling instruction, including teaching proportional reasoning, could aid conceptual understanding of chemistry concepts regardless of a student's previous math ability. Modeling instruction was implemented in 20 sections of high school general chemistry classes. Data were collected from 110 students and 4 teachers in the form of observations, conversations, and surveys. Data were coded using an open coding system to find themes. Findings were that modeling instruction, developed by the American Modeling Teachers Association, emphasizes active student engagement through collaborative learning, inquiry-based learning, and the development of conceptual understanding and provides a way to demonstrate mathematical thinking without the use of a sense of algebra. By adopting this approach, educators that teach a general student population can create a deep understanding and appreciation of chemistry without the necessity of a solid mathematical background. Recommendations for further research included an analysis of chemistry curricula at the middle school, high school, and college levels to develop and evaluate new curriculum materials that explicitly emphasize proportional reasoning concepts. This could include a longitudinal study to track students' development of proportional reasoning skills over time. Another recommendation was to investigate current chemistry teacher certification programs for the inclusion of proportional reasoning methods and for the impact of professional development programs on educators. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]