Street Magic — Tamora Pierce

It's been four years since Briar Moss began his training as a plant mage, but he still hasn't put his past behind him. Wandering through a Chammuri market, Briar comes across a street girl using powerful magic to polish stories for a merchant. He resolves to find her a teacher. But Briar understands the city's gangs as well as he understands Evvy, the young mage. When gang warfare breaks out in Chammur, Briar has sympathy for those caught in the crossfire. Then he discovers that the fiercest gang is seeking a stone mage to lead them to hidden gems. Briar once believed gangs offered protection, but now he and his magic may offer the only protection Evvy can count on. As Briar is swept up in a bloody conflict, he must decide whether he's ready to make the final step away from his former life as a "street rat."