This paper examines the possibilities of designing a formative assessment that gathers information about novice elementary teachers' skills with modeling content and makes sense of such information. A decomposition of the practice of modeling content was developed and used to design the assessment. Participants included ten first-year teachers who graduated from a range of different teacher education programs. The findings reveal that our formative assessment works to gather information about teachers' capabilities with modeling content and that the associated tools support making sense of the information gathered. [For the complete proceedings, see ED630210.]