Current researchers have not been clear on whether or not professional development expenditures, at the school district level, share any possible relationships with student achievement outcomes on state-level summative testing. While there are many articles and numerous research studies on the concept, they are very contradictory in their findings. The purpose of this quantitative, correlational study is to test the theory that increased spending in district-level professional development expenditures is related to district-level student achievement scores in ELA and mathematics. The researcher examined the 518 public schools within the State of Missouri. The researcher also examined the relationship between professional development expenditures and district-level student achievement scores (proficient and advanced(percentages) in ELA and mathematics on the Missouri Assessment Program (MAP), for the school years of 2017-2019. Based on study results, there are a few professional implications that can be quickly identified by the negative relationship indicated by the Pearson r between district professional development spending and student achievement scores. There were no statistical relationships indicated by the Pearson r coefficient between district professional development spending and student achievement scores for the subject of 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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]