BlocksCAD Easy, Open-Source Solid CAD for Everyone!
BlocksCAD is a drag-and-drop 3D Computer Aided Design and modeling tool designed for use by elementary-age children. It is simple enough to learn in a few short hours of instruction, but still has the features, flexibility, and power of a professional-level program. It was developed at Einstein’s Workshop, a hands-on learning center and kids makerspace in the Boston area.
Source: BlocksCAD