Low-income college students face costly moral choices between pursuing their personal academic success and fulfilling their family responsibilities. They almost certainly face these choices more frequently and at greater personal cost than their faculty recognize. This article explores the sources and nature of that professorial lacuna; the article argues that this moral oversight results from the fact that middle-class people and low-income people often practice family in subtly but significantly different ways. They tend to emphasize different moral norms (independence vs. mutual aid) which shape the qualitative nature of college students' obligations within their families. They also tend to utilize different family structures (nuclear vs. complex and extended) which create quantitative differences in the number of people to whom family responsibilities can attach. The paper ends with a practical implications section that discusses ways to address this lacuna so instructors can gain insight about their students' familial obligations.