In this paper, Sonia Nieto develops the thesis that teaching is political work, by showing how issues of power and privilege are involved in all aspects of education--from classroom practices to infrastructure, from testing issues to decisions about curriculum. At the center of the educational process stands the teacher, and teachers can make a difference. Drawing on her research, Nieto describes the qualities of teachers who make a positive difference in the lives of students, particularly those students who have been marginalized. These qualities can be summarized as: a sense of mission; solidarity with, and empathy for their students; courage to challenge mainstream knowledge; improvisation; and a passion for social justice. [This paper was produced by the Child Development Institute at Sarah Lawrence College.]