School interventions are often based on the assumption that such variables as self-concept and locus of control should have a meaningful impact on achievement. Yet research support for such influence is inconsistent. Because this inconsistency may be due to methodological problems, a study was conducted which used path analysis to determine the relative influence of self-concept and locus of control on achievement, while controlling for other influences. Data were obtained from a sample of the high school seniors (N=22,660) from High School and Beyond, a nationally representative longitudinal study of educational efforts. Variables representing race, family background, intellectual ability, self-concept, locus of control, and achievement were entered into a path model, which was solved using a series of multiple regression analyses. The results suggest that intellectual ability has the strongest impact on achievement, and that locus of control also has a meaningful impact. General self-concept seemed to have a meaningful impact on locus of control, but no meaningful effect on achievement for this age group. These findings suggest that, at least for high school students, the improvement of general self-concept may not be an effective means of improving achievement. Programs designed to produce a more internal locus of control, however, may have a positive impact on achievement. (NRB)