Part I of this report describes the responses that 50 individual teachers and 72 small groups gave to the data scenario questions. The teachers interviewed are not a nationally representative sample, but they do provide a detailed initial look at how these particular teachers think about student data in schools that were thought to be ahead of most schools in the nation with respect to data use. This detailed description of teacher thinking can help inform those responsible for training teachers in data-driven decision making about the kinds of difficulties and misconceptions teachers are likely to encounter. Part II of this report provides material that can be used in training teachers on the use of data to guide instruction. It contains the seven data scenarios used in the exploratory substudy, along with guidance on how a professional development provider can use the scenarios as part of teacher training or teacher learning community activities and the particular points that should be looked for in teachers’ responses to each scenario.