TinkerCAD is a web-based, entry-level modelling platform that is entirely free, with an education component that allows teachers to create and add students to classes so that they can then see the designs students create. Students don’t need to login in, although they can create accounts using their school emails which will then allow them to retain their designs from class to class and year to year.
Check out the guides below for help with signing up to TinkerCAD, creating classes, joining a class (for students), creating designs, and exporting your designs for 3D printing.