This paper documents the widely perceived but little investigated notion that teachers today are less qualified than they once were. Evidence of a marked decline in the quality of young women going into teaching between 1960 and 1990 is presented, using standardized test scores, undergraduate institution selectivity, and positive assortative mating characteristics as indicators of quality. In contrast, the quality of young women becoming professionals increased. The Roy model of self-selection highlights how occupational differences in the returns to skill determine teacher quality. Estimates suggest the significance of increasing professional opportunities for women in affecting the decline in teacher quality.