While utilizing assessment data has been a pervasive practice in educational reform for decades, and teachers are expected to use assessment data to improve instruction, little is known about how the practice of requiring teachers to review test data affects their perception of effectiveness in addressing the learning gaps of student groups. This qualitative phenomenological research study used open-ended, semi-structured interviews to help better understand how the expectations of teachers analyzing and integrating assessment data translates into teacher instructional practice and self-efficacy. This study aimed to explore the shared experience of teachers required to participate in collaborative planning centered on analyzing common test data. The study also explores common barriers to integrating assessment data into classroom lessons, deficit-thinking triggers, and effective practices for facilitating data meetings, and identifies which types of data teachers find helpful to inform their teaching practice as they work to improve outcomes for their equity student groups. The findings show the practice of having teachers collaboratively review summary test data, also used for accountability and district monitoring, is not perceived by teachers to increase their efficacy in addressing the compounded needs of equity student groups and may encourage deficit-thinking. The study also found specific practices teachers perceive as effective when looking at assessment data to improve instruction for the equity student groups. [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.]