TinkerCAD remains one of education's leading 3D design tools.  Completely free, easy to use with mostly click-hold-drag manipulation, and easily connects to Google Classroom rosters for viewing students' designs.   Try it out for yourself, ask one of your ITS to come in and teach your kids, or just let them learn in an exploratory manner.  Either way, it's abilities will provide foundational 3D design skills that will easily translate into almost any work or education field!