Each item of the Rotter Locus of Control Scale and 28 of the 80 items of the Piers-Harris Children's Self Concept Scale were revised because of syntax or vocabulary that were considered to be problematic for deaf adolescents. The original and modified forms of each instrument were administered to 90 deaf adolescents from four residential schools. Better prediction was obtained for six of the nine subscales of the Stanford Achievement Test for the Hearing Impaired when scores from the modified forms of the instruments were used as predictors in place of scores from the original forms of the instruments. Other predictors were parent hearing status, sex, age, and school. Generally, parent hearing status and self concept were the most important predictors of the achievement subscales; however, the increase in prediction that occurred when the modified forms of the instruments were used as predictors was due particularly to the locus of control variable. Tables with statistical data are appended. (Author)