This dissertation discusses the relationship between teacher sensemaking, attributions, and instructional adjustments prompted in response to student performance data. Through this qualitative observation study, this paper explores the varying perspectives of teachers, including their level of assessment literacy, and the dynamics of their Professional Learning Community (PLC) teams, and how they impact the teachers' perceptions of student performance data. Furthermore, this research examines how leaders in the field can leverage the insights gained from teachers' sensemaking processes to better support them in the context of a PLC. This dissertation aims to contribute to the research surrounding teacher sensemaking and attribution theory to gain a deeper understanding of factors that influence instructional decision-making. [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.]