Educational leaders throughout the United States have repeatedly emphasized the importance of increasing the number of Black and Latinx teachers in American schools. Prior qualitative work suggests that Black and Latinx teachers who are demographically isolated in their schools often report negative experiences. Drawing on theories of proportional representation in organizations, we use Tennessee statewide survey and administrative data to examine whether self-reported professional experiences of Black and Latinx teachers are different when they are demographically isolated. We estimate models using two measures of demographic isolation: a continuous measure and a theoretically generated ordinal measure. We find that, for Black teachers, the percentage of Black teachers in the school is positively associated with teachers' perceived satisfaction and support and with the frequency of collaboration. There is also some evidence of threshold effects of demographic isolation for Black teachers, as Black teachers in schools in which at least 60% of fellow teachers are Black report significantly higher satisfaction and support than other Black teachers. Our models do not find any associations between isolation and professional experience for Latinx teachers, but a small sample size and lack of variation in demographic isolation among Latinx teachers makes it difficult to estimate these associations. Our findings suggest that both ordinal and continuous measures of demographic isolation may be useful when examining relationships between demographic isolation and workplace experiences. Because we study factors linked to turnover in prior research, these analyses can contribute to the broader discussion about the retention of Black and Latinx teachers.