Within psychology, efforts to address racial-ethnic disparities in students' academic outcomes have focused primarily on students themselves. But there is another important person in classrooms: the teacher. In the United States, most racial-ethnically minoritized students are taught by White teachers. Drawing on research on cross-race interactions, we argue that for White teachers--especially those new to the profession--this dynamic is likely to elicit psychological threat, which then undermines their relationships with students, their well-being, and their effectiveness as an instructor. We hypothesized that values affirmation, a technique to mitigate threat and stress, could improve these outcomes. We randomly assigned White public school teachers (N = 109) at schools serving predominantly minoritized students to complete a values affirmation exercise or a matched control exercise in the fall of their first year of teaching. Five months later, affirmed teachers reported greater well-being and better teacher-student relationships than their control counterparts, and their classrooms were rated as more rigorous and more supportive of students' academic growth by trained observers.