Drawing from an ethnographic study of how one school community negotiates English-only policy in Arizona, we investigated how a bilingual community of practice was established at one school. Integral to establishing this bilingual community was the mobilization of Spanish-speaking families in the school's daily life and operation. This school-parent mutual engagement cultivated feelings of "confianza," or trust, between educators and families, and ultimately facilitated the use of parent waivers to opt out of the state's mandated English-only program. Implications include the significance of establishing bilingual communities of practice and the need to engage the entire school community, especially families, in policy negotiation.