Assess educators’ ability to guide students to enumerate and analyze all unique part–part–whole (number-bond) decompositions of each whole number 1–20 using physical manipulatives and visual models. For each number: list all unordered pairs of whole-number parts (include 0 and the whole), represent each decomposition with counters, ten-frames, number-bond diagrams or bar models, demonstrate a reliable strategy to generate every decomposition without duplication, and provide instructional prompts to help Pre-K–Grade 2 learners reason about results. Finally, analyze patterns across numbers (counts of decompositions, parity effects, relationship to halves, complementary pairs) and justify how your manipulative-based activities support those analytical observations.