The Black Witch by Laurie Forest

Written by a Vermont author. Check! Impressive world building, along with intriguing folklore within different cultures. Check! A magical school. Check! If this hits every checkpoint in your list (as it did on mine), I highly recommend this series with every fiber of my being! And I cannot get over the magic. Oh my goodness, the magic! The magic system itself is so original and intriguing. so much so that I devoured this book in a single day! And I continue to steamroll through the rest of the series. I cannot recommend this series enough.