Ethnic minority students are at risk for school failure and show a heightened susceptibility to negative teacher expectancy effects. In the present study, whether the prejudiced attitudes of teachers relate to their expectations and the academic achievement of their students is examined. The prejudiced attitudes of 41 elementary school teachers were assessed via self-report and an Implicit Association Test. Teacher expectations and achievement scores for 434 students were obtained. Multilevel analyses showed no relations with the self-report measure of prejudiced attitudes. The implicit measure of teacher prejudiced attitudes, however, was found to explain differing ethnic achievement gap sizes across classrooms via teacher expectations. The results of this study also suggest that the use of implicit attitude measures may be important in educational research.