SketchUp is a powerful 3D CAD program that is simpler for students to learn than many other Professional CAD software. Models are created by drawing 2D shapes on one of the 3D planes then pushing and pulling the shapes into 3 dimensional forms. Shapes can be moved and grouped to build up the 3D drawing.
We recommend SketchUp for students in upper KS2 and upwards although younger students will need support in checking and preparing their models for 3D printing. One drawback of SketchUp is that it is not straightforward to produce a 3D printable model file from a design as it is a surface modeller. However once students are familiar with the process for checking and preparing the file they should be able to do this independently. To help you with these steps, iMaterialise have produced a really useful article for 3D Printing with SketchUp. It may also be worth considering using SketchUp alongside Meshmixer for preparing the 3D model files.
SketchUp is desktop software, available as a free download for educational use. To access the software, you download the free trial and select the “SketchUp Make” version. The free trial includes the Pro version of the software, but reverts back to the free Make version at the end of the 30 day trial period. You can also apply for free one year educational licenses for the Pro version.