I would suggest LB+HB (Ladybug and Honeybee) tools for your purpose, because of the following reasons:
-They are free and open-source and easy to download and start
-They work within the Grasshopper environment which enables students to interact their parametric models with thermal, solar, energy, daylighting aspects.
-Basically LB+HB serve as a hub to connect the Rhino/grasshopper model with a number of professional engines and platforms such as EnergyPlus, OpenStudio, Therm, etc.
In the case of solar and shading analysis I would highly recommend SOLARCHVISION tools, however not sure if it's possible to use them free but there are books and articles about them which would help students to find robust understanding about the sun, climate and their effect on the built environment.
I would recommend Diva for Rhino and Grasshopper, and there two reaseosns why I'm recommending Diva
1- Although Diva doesn’t have too many options, It's a lot easier to use than Honeybee and Ladybug, so it's suitable for beginner students who are just starting to learn thermal performance.
2- Unlike HB, Diva works with Rhino, so students who aren't familiar with Grasshopper can use Dive
In addition to the two reasons I mentioned, it's free for students.
Personally, I prefer HB over Diva, but HB might not be the best choice for beginner students