This case study reports on a mixed methods research study that investigated high school students’ beliefs and belief justifications about a controversial issue in their city. We used an explanatory sequential design, which begins with the collection and analysis of quantitative data, followed by the subsequent collection and analysis of qualitative data. The researcher then uses the qualitative data to explain some aspect of the initial quantitative results. A key feature of this design is that the researcher uses quantitative findings to establish criteria for purposefully sampling a subset of participants for follow-up interviews. We provide an overview of the study and describe the key decisions we made in conducting and communicating the study. We provide insights into the decision-making process we used with an aim of helping researchers consider key decisions that are made, and the justification for those decisions, in the planning and implementation of an explanatory sequential mixed methods study as well as the write-up of the manuscript for publication.