Blender is the free and open source 3D creation suite. It supports the entirety of the 3D pipeline—modelling, rigging, animation, simulation, rendering, compositing and motion tracking, video editing and 2D animation pipeline.
It is installed on the school computers but if you are using your own device you will need to install it from the blender site - https://www.blender.org/
It's technically possible to install it on a Chromebook:
https://chromeunboxed.com/three-ways-to-install-blender-3d-software-on-your-chromebook/
SketchFab Add-On
https://projects.raspberrypi.org/en/projects?software%5B%5D=blender