This quantitative research study of first-grade students in two rural school districts sought to understand the difference, if any, between teachers' professional development training in the science of reading and student achievement. The study also examined the statistical relationship between the science of reading professional development and students' mean scaled reading scores taken from the i-Ready Diagnostic and Screener three times during the school year. The researcher analyzed data with t-Tests and Pearson's Correlation. The study results indicate that the science of reading professional development did provide statistical significance between students' mean scaled reading scores. However, no relationship between professional development and students' achievement scores in reading was observed. Although many variables exist in education, the study did show an increase in mean scaled reading scores and can arguably be a positive variable for increasing student achievement over time. Further study is encouraged. [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.]