Rochelle Gutiérrez has spent 15 years researching effective, urban high school mathematics departments that served Black, Latin@ and low-income adolescents (see, e.g., Gutiérrez, 1996, 1999a, 1999b, 2000, 2002). These were schools where students took more mathematics than was required by their district; where English learners, recent immigrants, and students who juggled childcare took college preparatory mathematics courses; where historically underserved and/or marginalized students scored better than their peers on standardized tests of mathematical achievement; where a large percentage of seniors took calculus; and where high achieving students reflected the demographics of those who attended the school. Among other things, Gutiérrez found that their teachers met regularly (inside and outside of school) to discuss students, teaching, and mathematics; worked hard to recruit like-minded staff and to socialize new members into a strength-based perspective on students; strategized collectively to eliminate low-level courses; interpreted creatively (or simply bent) the rules to fit the long-term needs of their students; convinced colleagues of students' capabilities; refused to enact discipline policies that kept students out of the classroom; and twisted students' arms to take advanced mathematics courses. In essence, these teachers negotiated the politics of school reform, language, racism, and testing (Gutiérrez, 1999a; Gutiérrez, in preparation a; Gutiérrez & Morales, 2002). Despite recent researchers making significant gains in extending the knowledge bases to better address the needs of Black, Latin@, American Indian, and low-income youth, the political component of teaching is still largely missing from discussions of important knowledge that teachers need. In this commentary, Gutiérrez highlights some of the ways that both mathematics and mathematics teaching are political. She then argues that educators in general, and mathematics educators in particular, must expand what is considered to be necessary knowledge for teaching, adding political knowledge for teaching. Finally, she shares what she has learned from supporting mathematics teachers to develop political knowledge and to advocate for historically underserved and/or marginalized youth.