Here is a student friendly 5th grade opinion writing rubric. This is an editable word document for you to customize to your liking. I have a first read grade and second read grade option listed. After my first read, I give the essays back to students, so they can see what sub-standards they should work on.Then they turn the essay in a for a second read with the corrections and improvements made for a final grade. This also helps to facilitate differentiated writing instruction where groups opinion writing.
I also have the following rubrics available and a bundle of all three genres below.