This paper presents the results of a study to investigate the effects of including an assessment of adaptive behavior, the Adaptive Behavior Inventory for Children (ABIC), in classifying students. Children in this study were either referred for or currently receiving special education services in a tri-ethnic district of 40,000 students. Three approaches to classification of "mental retardation" were compared, based on a small number of students from the three racial and ethnic groups (Anglo, Black and Mexican-American) and from middle and low socio-economic status (S.E.S.) backgrounds. Results indicate that the pluralistic approach (a combination of psychometric assessment and adaptive behavior) results in the smallest number of students being labeled mentally retarded. This was reflected primarily in re-classification of low S.E.S. Mexican-American students at the educable mentally retarded range. Implications for re-classifying these students are discussed, and modification of existing categorical classification systems is recommended. (Author)