Currently, a knowledge gap exists at the intersection of immigration, citizenship, and education. We have little knowledge of how teachers teach about citizenship when they anticipate that some of their students are undocumented. Conceptually, we distinguish between formal and cultural citizenship and draw from immigrant political incorporation theories. We investigate how high school civics teachers navigated the tensions of teaching youth in settings meant to socialize them for future political participation when some students did not have formal citizenship rights. Based on 88 hours of observational and interview data, we analyze three cases of U.S. government teachers selected from a pool of 39 secondary social studies educators. We ask: How did skilled and experienced civics teachers who supported immigrants' rights teach about elections in mixed-citizenship settings where some youth had formal citizenship rights and others did not? We argue that key features of teaching in mixed-citizenship classrooms were context, safety, and legitimacy. We also generate a set of propositions to be tested in future research. As scholars increasingly discuss what civic education should look like in light of immigration and globalization, we offer grounded perspectives about the situated roles of teachers in mixed-citizenship contexts. Understanding how skilled and experienced teachers address the possibilities of inclusion despite structural exclusions opens a window into how schools can be sites that defy the formal boundaries of citizenship.