The worldwide push for computing education at younger ages requires that teachers are prepared to deliver instruction that supports all learners. Other discipline-based education research fields offer a wealth of instructional scaffolds worthy of exploration in computing. One such scaffold drawn from math education is diagramming. While diagrams are frequently employed in university computing, little is known about its applications in K-8 (ages 6-14) computing.

To inform diagram design for K-8 computing, we investigated how the spatial orientation of a diagram (horizontal or vertical) influenced the extent to which K-8 teachers developed different technological, pedagogical, and content knowledge (TPACK) of computational thinking (CT) concepts, such as loops, conditionals, and decomposition. We found that more teachers were able to decompose a sequence of events when using a vertical diagram. While teachers in both conditions were similarly able to describe various CT concepts and aspects of TPACK, more teachers using a vertical diagram made connections between concepts, whereas more teachers using a horizontal diagram described concepts in isolation. We hope this exploration will spur future work into diagramming and more broadly, spatial reasoning in K-8 computing.