The School’s administrator will need to deploy SketchUp for Schools before students and teachers at that School will be able to launch the application. Once deployed, the SketchUp for Schools icon will appear in the Google navigation menu (at the top right of Gmail) and can be launched directly from there.
Is the “SketchUp for Schools” that is available through G-Suite a very old version from the olden days when SketchUp was a Google product? Or is it an alternate way of delivering a current SketchUp product attached to an educational license?