When teaching engineering design, sketching is a key element of design thinking that facilitates connection of hands and minds. As engineers use various graphical illustrations to conceptualise, communicate, and record design ideas, students make sketches to develop their design ideas. However, sketching instructions in engineering education often highly focus on technical drawing rather than strategic sketching. The study made three observations of sketching instructions from fourth-grade elementary science classrooms with two different sketching strategies and one control. The first group was instructed with effective uses of schematic symbols, the second group was introduced to a 2D template that showed the layout of the design product, and the third group was the control group. The study captured students’ design processes using video and audio records and sketching outcomes. The results showed that teaching young students the strategic use of schematic symbols helped generate high-quality design sketches and effective design cognition. The group that used a 2D layout also produced quality design sketches and more diverse design strategies compared to the control group. The results can inform science and engineering educators that sketching instruction for young students must shift to facilitating design thinking in order to eliminate cognitive overload in sketching.