Teacher data use is often centered around standardized testing. Such data use that is commonly centered on standardized tests and used during professional development does not necessarily transform teacher practice toward equity and fails to change teacher conceptualizations of students while also perpetuating inequitable practices. Conversely, the use of multi-dimensional data centered on equity supports teacher opportunities to build agency and ultimately transforms teacher practice toward equity. Although there are recent studies on data-based decision models, the culture of data use and teacher discussion of data needs to be more intentional about teachers' equity-focused sensemaking during professional learning. This study explored two teacher data use contexts and how each context yielded contrasting outcomes to teacher conceptualization of students and the impact on teacher practice. Using two theories, Humanizing Pedagogy and Attribution Theory, this study examined how professional development centered on data use--particularly what data are used, how professional development is designed, and the support structures required--leads to equitable changes in practice. Humanizing Pedagogy illuminates the need to shift teacher data use from standardized testing toward conceptualizing students as holistic learners. Attribution Theory describes different kinds of motivation to change teacher practice as teachers examine data from their students. This multi-case study features 3 teachers from 3 different districts who experienced data use in their site-based staff development (SBSD) and participated in the Student Work Analysis protocol within the Elementary Science Partnership (ESP) grant. Findings showed that, at these sites, teachers looked at scores that led to more inequitable conclusions and accepted the situation "as is" during SBSD. On the contrary, in ESP, these teachers examined student work, looked more deeply into student context and learning, and, thus, moved away from common deficit-based discussions that led to commitments to change their instructional practice. This study has implications for improving professional development by deeply considering how teacher data use should look to support an asset-based lens in students as well as building teacher commitment to shift practice. It also lifts the work needed to identify education data sets and how to frame professional development for teachers to improve instruction for marginalized students, which needs to be a priority to eliminate the opportunity gap. [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.]