ThreadHelp! I'm teaching a HS Video Game Design course this year.
How did this even come around if you don't know anything about game design? haha.
There are some great books out there such as Steve Swink's Game Feel and A Theory of Fun for Game Design by Raph Koster.
There's tutorials out there for game design and game engines from people like Tom Francis, Derek Yu, Rami Ismali and other really inspirational creators.
You already are off to a good start if you don't mind what the students use (Mario Maker editor) to show their design prowess. Try to get them to focus on core principles of design and less on what the actual games are or what they look like.