Political scientists have noted that, in a variety of communication settings, people are less receptive to information that comes from a politically disagreeable source. Yet, there is little research on patterns of communication across lines of political difference in an educational setting, which we argue is unique in a number of ways. Using a large-scale national survey of college students enrolled in political science courses, we examine how perceptions of professors' political orientations contribute to student learning, interest in politics, and effort in the course. We consider both direct effects of partisan difference on education and indirect effects, which work through a number of source credibility measures. Our analysis indicates that students who believe their professor to be a political ally report more learning, higher levels of effort, and greater interest in the subject than those who believe their professor to be a political foe. (Contains 4 tables and 4 notes.)