Personally, if I had my druthers, I'd try to associate Wizard schools with the ideas of various IRL traditions of magic. Something like...
The School of Runewrights
These Wizards tap into the power of language, that code which even on its own has the mundane magic of preserving meaning across the centuries. Runewrights naturally favor spells involving symbols, communication, etc., but they can also employ mystic runes to ward areas, call down devastating assaults, or give binding oaths magic power.
The School of Ink and Quill
Calligraphy is practiced in almost all civic societies, and even many non-civic cultures often develop an appreciation for these arts and other pictomancy. But calligraphy is not simply a way of making art; it can also bring magical effects to life...or bind life in magic ink. Such "Ink Mages" can draw forth powers and inkbound spirits, and preserve objects in pictorial stasis with their artful magic.
The School of Cartomancy
Draw the cards, quester, and hear what Fate may hold, for the magic of the cosmos flows through so-called "chance." There are those who turn the title "fortunte-teller" on its head, and tell fortune what shape it should have, delaying the foul until it can be weathered and prolonging the fair that it may grant greater boons. Time and truth and tempest too, but a turn of tousled tarot away...
The School of Mana
All things carry mana, that mystic substance which girds and heartens life. But your mana must be guarded, fostered, lest it be sapped or corrupted. Wizards of Mana learn the hidden rules which guide the flow of mana, and condemn those who break these tapu to suffer that loss. Bolstering allies and enervating foes, students of mana are as helpful as they are dangerous.