Tenure-track faculty play a special role in society: they train future researchers, and they produce much of the scholarship that drives scientific, technological, and social innovation. However, the professoriate has never been demographically representative of the general population it serves. For example in the United States, Black and Hispanic scholars are underrepresented across the tenure-track, and while women’s representation has increased over time, they remain a minority in many academic fields. Here we investigate the representativeness of faculty childhood socioeconomic status and whether it may implicitly limit efforts to diversify the professoriate in terms of race, gender, and geography. Using a survey of 7218 professors in PhD-granting departments in the United States across eight disciplines in STEM, social sciences, and the humanities, we find that the estimated median childhood household income among faculty is 23.7% higher than the general public, and faculty are 25 times more likely to have a parent with a PhD. Moreover, the proportion of faculty with PhD parents nearly doubles at more prestigious universities and is stable across the past 50 years. Our results suggest that the professoriate is, and has remained, accessible mainly to the socioeconomically privileged. This lack of socioeconomic diversity is likely to deeply shape the type of scholarship and scholars that faculty produce and train.