The purpose of this study was to explore how school leaders address both the technical and professional socialization needs of teachers during the planning and implementation of student formative assessment in every classroom, an initiative that is often implemented as a means of gathering the data needed to support the academic needs of all learners (Black & Wiliam, 1998; Bolman & Deal, 2008; Heath & Heath, 2010; Leithwood & Seashore Louis, 2011; Wiliam, 2010). In order to determine school leadership considerations for addressing the technical and professional socialization needs of teachers during the implementation of student formative assessment in every classroom, two research questions guided the study: 1. What do teachers perceive to be their technical and professional socialization needs experienced during the planning and implementation of student formative assessment and how are these met? 2. What are the school principals’ perceptions of how they address the technical and professional socialization needs of teachers during the planning and implementation of student formative assessment? Using a grounded theory approach, this qualitative study examined the perceptions of both teachers and principals through a multi-site case study design (Miles & Huberman, 1994). This design was chosen in order to gather insight regarding the perceptions and experiences of principals and teachers at three elementary campuses that have implemented student formative assessment in every classroom. The sites and participants for this study were purposefully selected. Data were collected through interviews and focus groups. In order to confirm emerging theoretical explanations, the researcher gathered additional data through a review of relevant documents, such as district and campus improvement plans. The prominent technical needs identified by teachers in this study were the development of a campus-wide common terminology, participation in vertical teaming, and the maintenance of the support role of a campus instructional specialist. Furthermore, teacher participants identified their professional socialization needs as reassurance from the principal with new professional learning, a gradual pace of implementation for the student formative assessment initiatives, meaningful teacher-to-teacher interaction, open and transparent communication with the principal, and opportunities to participate in building cohesive grade-level teams. Principals perceived their technical supports as facilitating vertical teaming, providing a campus instructional specialist, embedding time for collaborative professional development, and setting clear expectations for implementation. Additionally, principals perceived their professional socialization supports for teachers as facilitating the building of cohesive grade-level teams, providing reassurance with new implementation, promoting open and transparent communication, promoting a gradual implementation pace and facilitating meaningful teacher-to-teacher interactions. / text