Formative assessment is a classroom practice that has received much attention in recent years for its established potential at increasing student learning. A frequent analytic approach for determining the quality of formative assessment practices is to develop a coding scheme and determine frequencies with which the codes are observed; however, these frequencies do not necessarily reflect the temporal and sequential nature of teacher-student interactions. In this article, we explore the utility of sequential analysis as an alternative strategy to capture the nature of informal formative assessment interactions that take place in whole-classroom conversations as compared to frequencies alone. We coded transcriptions of video recordings of four middle school science "teachers'" whole-class discussions about density for different types of teacher statements associated with effective approaches to formative assessment, as well as the quality of the ideas students shared. Using sequential analysis, we then calculated transitional probabilities and odds ratios for those sequences. Results indicate that sequential analysis revealed differences across the four classrooms analyzed, particularly with respect to the way teachers responded to different kinds of student ideas. Recommendations are framed for the future use of sequential analysis in studying formative assessment classroom practice.