Peer assessment is an underutilized tool in mathematics classrooms. We examined how peer assessment could be used in a mathematics course to improve mathematical communication and mathematical proficiency. To describe in what ways peer reviews compared to teacher reviews, we analyzed ratings and feedback of 32 6th graders and their mathematics teacher. To determine what impact receiving peer versus teacher feedback had on students, we compared the revision quality and mathematical problem-solving abilities of students who received feedback from four peers to those who received feedback from their teacher. The findings indicated that middle school students can provide feedback just as helpful in improving mathematical communication and problem-solving ability as the teacher.