CRA Model . The CRA (Concrete-Representational-Abstract) model is a research-based instructional framework in mathematics that supports students in developing a deep understanding of mathematical concepts. . It begins with the Concrete stage, where students use physical manipulatives (e.g., blocks, counters, or number mats) to explore mathematical ideas. Next is the Representational stage, where students transition to drawing or using visual models such as number lines, ten-frames, or bar models