When students are aware of the exam grades of their peers, does this information affect their subsequent exam performance? For example, knowing that my friend scored a higher grade on Exam 1 than myself might motivate me to improve my performance on Exam 2, or might frustrate me such that I stop trying to catch up. We analyze whether students' performance is shaped by the grades of their classmates. To answer this question, we use survey-based data on students' connections to other students with the grades that students obtained in a class. We find that a peer effect on grades does exist, where students who know that the grades of their friends were higher than their own on the first exam are motivated to improve their score on the following exam.