A longitudinal study was designed to determine whether there were significant differences in academic achievement between senior high American Indian students in Federal on-reservation, Federal off-reservation, public on-reservation, and public off-reservation schools. The purpose of the study was to gather a variety of data on psychological and sociological variables and to investigate the relationship of those variables to achievement. A sample of students drawn from 21 high schools in 7 states was stratified on the basis of sex, grade, and geographic area, with approximately equal sex ratios. Tests administered at various times over a 4-year period (1966-70) were: the California Achievement Tests; the California Short-Form Test of Mental Maturity; the Mooney Problem Check List; a questionnaire to obtain personal and familial data; a semantic differential on attitudes; the School Interest Inventory; the California Psychological Inventory; the Value Orientation Scale; and the Vocational Aspiration Scale. No reliable differences were noted in terms of achievement between the 4 types of schools. For the 45 categories for which significant achievement differences were registered, rankings were so variable that no hierarchial pattern or evidence of particular superiority or inferiority emerged. Appendices include tables of mean scores of criterion and control variables with analysis of covariance and adjusted criterion means by school type and by geographic area. (FF)