Ethnic minority students face many disadvantages in school, which might be due in part to teachers' stereotypical expectations and attitudes. Dual process theories of impression and judgment formation specify person information that confirms or disconfirms stereotypical expectations as determinants of how judgments are formed. While expectation-confirming information should result in stereotype-based judgments, expectation-disconfirming information should lead to more information-integrating processes. Moreover, attitudes should also be affected in a positive way when a person encounters expectation-disconfirming information. The current study experimentally investigated these hypotheses with regard to stereotypical expectations about ethnic minority students. Eighty-three experienced teachers were randomly divided into four different groups. One group judged a below-average ethnic minority student (confirming) and another group a below-average ethnic majority student. Two other groups judged either an above-average ethnic minority (disconfirming) or ethnic majority student. When assessing a below-average student, teachers judged the confirming ethnic minority student as less proficient in language than the ethnic majority student. These differences could not be found for mathematical achievement or between the above-average ethnic minority and majority students. Attitudes toward ethnic minority students were not affected in the expected way. Findings are discussed with respect to their implications for future research.