With growing interest in supporting the development of computational thinking (CT) in early childhood, there is also need for new assessments that serve multiple purposes and uses. In particular, there is a need to understand the design of formative assessments that can be used during classroom instruction to provide feedback to teachers and children in real-time. In this paper, we report on an empirical study and advance a new unit of observational analysis for formative assessment that we call an indicator of a knowledge refinement opportunity or as a shorthand , KRO indicators . We put forth a new framework for conceptualizing the design of formative assessments that builds on the Evidence Centered Design framework but centers identification and analysis of indicators of knowledge refinement opportunities. We illustrate a number of key indicators through empirical examples drawn from video recordings of Kindergarten classroom lessons.