This study develops methods to measure student engagement in MOOC forums with peers holding differing political beliefs. Using a case study of the MOOC "Saving Schools," which explores education policy, the researchers find that, contrary to the notion of online echo chambers, students engage diversely and equitably with opposing viewpoints. Students interact directly through replies and upvotes, and they converge on a shared language in their discussions. The findings support the idea that MOOCs can fulfill a civic mission by fostering broad and inclusive engagement similar to traditional higher education.