The report describes a study designed to examine substitution between formal schooling and dropouts' post-school training or experience in the labor market. The basic hypothesis is that if formal schooling and post-school training are substitutes, then experience-earnings profiles measured in the logarithm of earnings should tend to converge. To test the hypothesis, a sample of approximately 11,000 males over 14 years, who had nonfarm earnings in 1966, and who were not in school or in the military, was selected from the Survey of Economic Opportunity conducted in 1967 by the Census Bureau. The sample was divided occupationally into eight subsamples (professional/technical; manager, official, proprietor; clerical; sales; skilled crafts; operatives; service workers; and laborers) on which linear regressions were run to determine the extent to which the post-school training of dropouts successfully substituted for the additional formal education received by high school graduates. The linear regressions revealed a very strong tendency for almost complete substitution to occur in all but two of the occupational groups (manager, official, proprietor; and skilled crafts). These tentative results lead to the conclusion that dropping out may be rational from the point of view of both the individual and society. (Author/JR)