Some thoughts:
This image might benefit from call outs. Maybe reformat what you can see into a numbered list, and add the numbers to the image? Also, what do you think about providing a little more context? For example, I'm guessing that each completed peer assessment (for and by this student) will be numbered and listed, but that's just a guess. Info about whether there is any way for staff to find out which students did a particular assessment might also be valuable in identifying students at the ends of the distribution: students who give super excellent thoughtful evaluations and students who give really unhelpful ones. (if you can't find out, that should be stated.)  
It's a really long image -- will it fit on one page of a PDF?