The purpose of this research is to explore the influence of a teacher and teaching practice, with a vision of social justice, on Latina/o students' learning of mathematics. This study builds on current understandings in the area of mathematics education, as well as on Latina/o students' academic opportunities. This study draws on a multi-level framework to explore Latina/o students' mathematical learning from a socio-historical perspective (Martin, 2000). The teacher's, students', and parents' perspectives are included throughout the process of inquiry. The data of this study are discussed in two focal points: the classroom community and families. The participants in the study are: eighteen fifth-grade students, the parents of four of these students, and the classroom teacher. I developed multiple case studies, including in-depth case studies for four students. The framework of communities of practice is an analytical tool that uncovers the learning of Latina/o students, as well as other students, within classrooms. It is a resource to inform suggestions to those making decisions on how to improve these cultural practices for Latina/o students. This study suggests learning is goal-oriented and identity is an integral component of learning in connection to the community. A collaborative environment is central to supporting students' identities as mathematics learners and critical mathematics citizens. Students' participation in the classroom community needs to include interconnections with their lived-culture (Gutierrez & Rogoff, 2003; Moll, 2000) and a critical lens embracing diversity as a resource. These connections support students' sense of ownership in the negotiation of mathematical meanings. Finally, through the in-depth case studies I identify those cultural beliefs that might have an oppressive effect on students and their communities, but also those that resist and counter deficit views that society bestows upon them (Martin, 2006). The analysis of the four case studies highlights five principles of families' participation in their children's mathematics education. I argue families' participation in their children's mathematics education is situated, historical, distributed, and mediated by power structures, and the cultural tools and values attached to them. This study points to the need for further research that connects schools to the communities they serve.