I suspect that maybe you're trying too hard to solve a problem that doesn't really exist by trying to "fit" each one to a set primary/secondary colour.
The wizard model would make it reasonably obvious (hopefully) what school of magic they belong to?
I mean, I can't say that purple suits an Illusionist better than any other school for example, since it depends on the model, the ratio of colours, etc.
So whilst I think making each one a bold main colour is a great idea, I wouldn't get too stuck on it if it means you have compromise on a colour scheme you like.
Another idea might be to pick one colour for each wizard, and then add to it the colours from aligned schools for accents? Again, not something you *have* to follow, but it might throw up some interesting colour combinations to work with?