To test a hypothesis that a positive improvement in attitudes and perceptions of Mexicans and Mexican Americans would result from a special curriculum unit pertaining to Mexican and Mexican American culture, 154 Anglo American and Mexican American children enrolled in 6 sixth-grade classes in Chandler, Arizona, were randomly assigned to control or experiment conditions for 4 weeks of special curricular study of Mexican culture. Teachers were allowed to implement the unit ("A Bicultural Heritage" by Schon) in their own style. The effect of the curricular study on perceptions of Mexican Americans was studied by having students respond anonymously to an attitude inventory. The perceptions of Mexican Americans by Mexican Americans were not highly positive; however, the perceptions of the Mexican American group were much higher than those of the Anglo group, whose responses were negative almost as often as they were positive. The means of all groups decreased progressively throughout the study, and the posttest means were significantly lower that the pretest means for all groups. Apparently, the promise of anonymity caused the students to feel more secure and free to express negative attitudes. Test results indicated that cultural and ethnic attitudes are developed over a period of years and may not be easily changed through short term curriculum development projects. (CM)