This study involved empirical investigation of a moves-based conceptualization of teacher practices of planning, enacting, and reflecting on formative assessment (FA) in mathematics classrooms in a high-needs school district in California. A qualitative case study of six middle school mathematics teachers' practices of "posing" questions, "pausing" to foster equity of participation and quality of response, and "probing" student thinking, the study provides empirical evidence of qualitatively distinct levels of teacher posing, pausing, and probing moves. The study utilized a National Research Council-based educational assessment design framework that employed construct maps, multi-faceted items design, and scoring guides to examine teacher practice and to provide feedback protocols for teachers engaged in FA. Guided by the 2014 "Standards for Educational and Psychological Testing," the study provides evidence for content validity and tools for future rater reliability investigations. The study found levels of teacher questioning practice, operationalized as posing, pausing, and proving moves, could be represented along generalized continua in the context of middle school mathematics instruction. The study's work toward the development of a teacher learning progression framework in the formative assessment domain has implications for establishing an empirically-based, common grammar of practice in mathematics instruction and preparation. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]