Interest in dashboards in schools has been growing in recent years as they have great potential in fostering data transparency and informing teachers' practices. However, research surrounding them is not unified and even less transparent, because of a lack of guidance in grounding their design as a process tailored to end-users needs. We present a process model for teacher-centered dashboards as a design and validation process with four mutually informed stages: (1) situate the domain space by framing teachers' routines, practices, and needs, (2) ideate the domain into multiple alternatives and prototypes, (3) develop, and (4) evaluate the dashboard. We drive recommendations within each stage to inform the process. We borrowed the foundations of the model from research in the HCI and InfoVis fields. We apply our model to five case studies from literature. We find that this model can provide a framework to scaffold dashboards' design process, mutually inform the underlying stages, and guide consolidating artifacts. We reflect on our work to provide design implications to point towards explainable dashboards design to best support teachers.