In this article, the authors describe the cyclical process of a collaborative evaluative inquiry project and the data collected throughout the project—data that not only informed "next steps" during the project but also show promise in documenting the benefits of such projects. Over a period of 18 months, seven elementary teachers from a K–6 urban elementary school collaborated with university personnel using Parsons’s (2002) Evaluative Inquiry Model, a 5-stage, cyclical model that includes defining, planning, and investigating challenges; collecting, analyzing, and synthesizing data; and communicating findings that transpire through collaborative inquiry. Overall, the project focused on improving the elementary teachers’ skills of inquiry and, in turn, their mathematics instruction and students’ learning outcomes. The long-term goal was to enhance teachers’ roles in their schools by affording them the opportunities to make informed decisions throughout their teaching based on an effective and skillful use of data.