In her school’s single classroom, she teaches children of various ages and grade levels who work in small groups at their own pace. Rather than standing by a blackboard at the front of the class, Ms. Mazzo moves among them, serving as a guide more than an instructor. Using this method, she has taught generations of children, the sons and daughters of local farmers and coffee growers, to read, write and do math. Her primary school students are often among the first in their families ever to have set foot in a classroom…