The goal of this paper is to support leaders in planning and reviewing their assessment implementations in the early grades. This paper will help readers with the following: - Understand the 'big ideas' from early childhood thought leaders--what do they believe should guide assessment decisions for the youngest school-aged students (prekindergarten through third grade)? - Discover what the research shows to be effective in terms of assessment in the early grades - Come away with a clear sense of next steps to apply the research and best practices to your own assessment planning process In preparing this paper, we reviewed key ideas from professional guidelines on early childhood assessment. To frame our analysis of these guidelines, we also addressed two topics: 1) background on assessment-related concerns in the early childhood field, and 2) evidence of the leverage that early education and intervention provide on later outcomes. In this context, we closely examined professional recommendations relating to assessment purpose and assessment method. Finally, taking these important considerations into account, we created three guides for best practices in the assessment planning process in the early grades. (author abstract)