This paper examines teachers' attitudes towards their students' heritage language maintenance and their engagement in classroom practices that may or may not affirm the value of maintaining and developing heritage languages among students. Through surveys and interviews with K-12 teachers in California public schools, the data show that the nature of teacher training and personal experience with languages other than English significantly affect teacher attitudes toward heritage language maintenance and bilingualism. Teachers who did not receive training as language educators expressed negative or indifferent attitudes toward heritage language maintenance and did not see a role for themselves and schools in heritage language maintenance efforts. This study highlights the need for all educators to better understand the critical role and functions of heritage languages in the personal, academic, and social trajectories of linguistic minority students. (Contains 3 tables.)