Controversies centering around the accuracy of the estimates made of bilingual children's intellectual functioning and the effectiveness of prescriptive programs recommended for their subsequent development have resulted in the investigation and assessment of different instruments used for student placement in special education classes. The three major tasks undertaken in this study were: (1) to compare results obtained using the Hiskey-Nebraska Test of Learning Aptitude (HNTLA), a test developed for use with deaf children, with those recorded using the Wechsler Intelligence Scale for Children (WISC) Performance Scale; (2) to determine the validity and usability of the HNTLA for bilingual school children, and (3) to re-evaluate a sample of Mexican American and Navajo children previously assigned to special education classes. Study results point up important differences between the correlations obtained for the Mexican Americans and the Navajo on both the test scores and the ratings by teachers, parents and subjects. The I.Q. levels on the HNTLA correlated with WISC I.Q.'s significantly better for the Navajo sample than for the Mexican American; the same was true when the HNTLA median Learning Age was compared with the WISC median Test Age. Since the standardization samples for both tests did not contain suitable numbers of either Mexican Americans or Navajos, neither instrument furnishes appropriate norms for these minority groups. (Author/BJG)