I just finished reading Od Magic, a 2005 book by one of my favorite writers; Patricia McKillip.
Od is a giant of a wizard of saves the kingdom of Keilor from it's enemies. In return, the king allows her to establish a wizards school. Generations pass until Od invites Brenden to be a gardener at the school. Brenden's arrival sets off a series of events which leads to a series of questions around magic, control of education, and expecting the unexpected. There's magic afoot that the wizards know nothing about.