Frames, trusses and beams, and why some structures stand while others fold, buckle or sag.
Design and Technologies (Engineering principles and systems) is the home; forces from Science and ratio and powers from Maths are applied, not taught. A pin-jointed truss model (members only pull or push; pushes buckle with length) and a pine beam model, both stated in each lesson's teacher notes. Spaghetti, straws or balsa make a good hands-on test to failure after the board.
Other pathways: Mechanisms · Physical computing · CAD and fabrication · Design your own board