Students also may worry about whether it is fair to be evaluated by someone who is not a teacher. If this happens, you can point out that they will be graded not on the reviews they receive, but on the thoughfulness of their responses to these reviews.
Students who are more accustomed to competition than to collaborative learning are likely to worry about plagiarism when asked to share their work. Once they overcome this barrier, students may discover that they can learn from each other in a process through which everyone benefits.
Inevitably, some students will receive peer reviews that are not substantive and helpful. A classroom discussion about this problem can be used to point out that this can occur in "real" scientific review as well, but that overall the peer review system does help scientists to improve their work.
Plagiarism is another possible concern for teachers. If students have access to completed research reports, either in the classroom or on the web, how can the teacher be sure that students will carry out their own work rather than simply copying someone else's? This concern is more valid with traditional "cookbook" lab reports than with reports of open-ended student research. In the case of EI student research, the student provides evidence of original work at each stage of the research process, from designing the experiment through presenting the results. Although it would be possible for a student to copy someone else's final results, this would be meaningless because the previous steps in the research process would be missing.