Biased assessment instruments and practices can lead to over-representation of minority children in special education classes. This paper analyzes the amount of variance in Mexican-American achievement test scores attributable to sociocultural factors. Fifty learning disabled Mexican-American elementary school students completed the Peabody Individual Achievement Test (PIAT) and Wide Range Achievement Test-R (WRAT-R). Their parents completed the Sociocultural Scales of the System of Multicultural Pluralistic Assessment. Sociocultural variables were not predictive of the total scores on the PIAT or WRAT-R. Some individual subtests of the PIAT and WRAT-R were significantly related to the Socioeconomic Scale or the Urban Acculturation Scale. In the latter scale, the Anglization factor was most important. These results suggest that the PIAT and WRAT-R are not discriminatory when used with lower socioeconomic or minority group children since a significant amount of variance could not be accounted for by sociocultural factors. This report contains 39 references. (SV)