Generally speaking, according to their philosophy, elves are neither servants of darkness nor preachers of light – they prefer harmony and balance between the two, a balance of all that exists. Hence the idea of giving them opposing schools such as Summoning and Chaos, but in reality, Light Elves without light are simply not Light Elves...
And by the way, here's another point: if the Empire worships a dragon of light, then what, pray tell, is the point of having dark magic in their guild...? :confused:
We need to come up with a more logical arrangement. Let's set aside the argument that "it's more useful for them in the game" and think about how we can distribute these schools.
1. I think it would be more appropriate to give humans Light and Creation (Summoning)...
2. Mages don't worship gods or pray to any spirits; they control them and use elemental magic, so they should have Summoning and Chaos.
3. Summoning and Darkness are a good fit for Necromancers (thankfully, this is perfectly clear).
4. Demons are a race of chaos, and quite villainous at that, so Chaos and Darkness would suit them.
Now, here's where it gets tricky:
5. Dwarves require fire spells from the Chaos school, but the second school is more problematic – they seem to have been given Light for some reason, but they need Summoning for their strategic use.
6. It's not entirely clear what to do with the Light Elves. They've always been associated with Summoning, but they haven't been given it here. Also, elemental magic suits them, so Chaos could be an option, although they are generally good and light suits them (personally, I'm leaning towards Light-Summoning, but that would be the same as for humans, and I'd like to avoid repetition).
7. The Dark Elves have been left without magic related to their god. They need Darkness, and they are experts in chaos, so Darkness and Chaos would be suitable, but that combination has already been used by the Demons, and the Light-Darkness combination is out of the question.

In general, with four factions and two schools each, there are six possible combinations, and there will inevitably be one repetition, so we can't avoid that...

This is my view; please share your thoughts.