Recent science educational reforms in the United States have prompted increased efforts to teach engineering design as an approach to improve STEM (Science, Technology, Engineering, and Mathematics) learning in K-12 classrooms. Teaching design in early grades is a new endeavor for teachers in the United States. Much can be learned from design teaching and research on K-12 design education outside of the US. The purpose of this study was to explore how students learn and use design sketching to support their learning of science and design practices. Researchers provided a treatment of design sketching instruction based on best practices of prior research finding (Hope in "Des Technol Educ Int J" 10: 43-53, 2005; Gustafson et al. "J Technol Educ" 19(1):19-34, 2007). A delayed treatment model was used to provide a two-group counterbalanced quasi-experimental design to compare an experimental group and comparison (delayed treatment) group results from (6) grade 3 classrooms. Researchers employed Hope's "Des Technol Educ Int J" 10: 43-53, (2005) frame to organize sketching data for analysis. Findings from this study indicated that design instruction treatment did improve student's design and communication practices, moving from using sketching as a container of ideas to the use of sketching as a form of design communication and to refine design ideas. Both the treatment and comparison groups improved sketching skills after treatment was provided to both groups. Sketching is a design practice that can also help student learn science concepts through the generation of mental models of conceptual understanding.