Answer:
It really depends. If the student that is peer reviewing is diligent in doing the task he/she is given, it may improve peoples writing style. Reviews of drafts may also help students in being able to critique others as well as give feedback, while building a relationship with the writer.
However, if the peer reviewer does not do a good job, then it would not help improve their writings.
A good review generally consists of at least one or more positive feedback, critique on any problems, some opinions on how to fix some issues, of course the basics such as spelling & grammar check, but the whole of the peer review is to give some other view, and trying to mold the essay into something better.
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