Really fun idea! An example of a challenge (drawing) might make clearer how they're used (personally found it maybe a little tricky to visualise - both the drawing and how they relate to flow of gameplay).
Prior to (or alternative) to grading, I think it could be fun to see if the teacher/other wizards could guess what the glyph/spell does before the creator explains it (feels like 'testing out' the glyph/spell do see if it works)!
These are both really great ideas! I think an example of play could certainly work to give a showcase on how to use magic to creatively solve a problem, I find seeing someone use a tool in a creative way really gets my ideas flowing.
An example I come to is needing to reach a floating island in the sky. Maybe you write a glyph with a Fly spell to try and fly up there, or a spell to create a pillar of earth tall enough to reach it.
As an alternative rule set, I think that a charades-like game of guess the spell could be fun for certain groups. Personally, I wouldn't want to include it in the core rules. Giving the artist time to explain their vision before examination helps to interpret their glyph in the best possible light, which is the intended goal of the design.
I get the connection between designing a glyph to reach a floating island - I think that's quite intuitive and is what makes the game so appealing! - it's maybe more the 'designing challenges' (four points - three challenges and a task, surrounded by a triangle of challenges, each line adds a feature etc etc) that I feel just maybe has quite a few steps that might be good to see examples of :)
And yeah, good point about group dynamics - can see that for players keen on a very thoughtful personal process, the rest of the group making silly guesses might not be much fun compared to being able to express themselves with clarity. (I maybe just lean more to the guessing type of play!)