This study investigated how teacher education assignments can be designed to support beginning teachers in learning to do the work of teaching. We examined beginners' formative assessment practices--in particular, their eliciting and interpreting of students' mathematical thinking--in the context of an elementary mathematics methods assignment, and the ways in which the scaffolds provided shaped their practice. We found that the scaffolds differentially supported their practice and suggest strategic improvement of the focus and organization of different types of scaffolds. Findings from the study contribute to the conceptualization and design of scaffolds for practice-based learning opportunities in teacher education. (Contains 3 figures and 3 tables.)