Data from Australia's Department of Employment, Education and Training were analyzed to determine the relationship between the costs and returns of secondary education in Australia. The analysis focused on changes in the following: the earnings premium from having a level of educational attainment equivalent to completing at least secondary school; the demand for employees who left school before graduation; full-time employment opportunities for teenagers; and the income support available to young people who stay in school. The earnings premium from having a level of educational attainment equivalent to completing at least secondary school was found to have increased in the 1980s after having declined in the 1970s. Changes in occupational structure and increases in the labor force participation of workers beyond their teens have substantially reduced the number of full-time jobs available for teenagers. Two other factors have also likely helped to more than double the rate of student retention in the final year (year 12) of secondary education since the early the 1980s: a long-term increase in the proportion of schoolchildren in part-time employment and substantial increases in government allowances for students who stay in school. (Thirteen tables/figures are included. Contains 50 references.) (MN)