Question, was the coop set up in such a way that parents are expecting you to give a final grade which is THE grade for that subject?
I ask because I felt like I was painted into a bit of a corner in the last coop I taught with. I taught the Intro to Literature course. A couple students struggled with the course, and did not complete all of the assignments. I gave all of the students the opportunity to revise essays to improve them. I gave incredibly detailed feedback on the assignments that were turned in. I gave out rubrics before the assignment and handed the filled out rubric back with the graded assignment. In the end I would have needed to give a D or an F to two of the students. I also had a couple students who were 8th graders taking the high school level class. They worked really hard, but still needed some experience with literary analysis and essay writing.
However, I also felt like some of the parents had signed up for the coop just as socialization or as an elective. I found out very late that one student was doing a full charter school course of study and the coop on the side. I didn't necessarily feel right failing a student given the overall setup of the coop, regardless of how little work they had put into the course. I was also one of the only coop classes doing a high school core subject.
What I ended up doing was giving out a grade report with a grade for each assignment listed as points possible for the assignment and the points earned. I broke this up with small weekly assignments, the year long allusions project, and all of the essay submissions. Each category had a total percentage and I calculated a class percentage. I also gave a list of the works used and a sample course description. However, I left assigning the final transcript grade to the parent. Partly because I didn't think the social contract at this particular coop included my giving a failing grade to the students. Partly because I recognized that a couple of the parents were going to put down whatever they wanted on their transcript anyway. Partly because I thought the failing was in part because the parents had not stayed involved in making sure their student was doing the work.
My grade report did have a couple suggestions as to how parents could use the assignment grades to produce a course grade. I suspect the parents of the students who did well just took my percentages and used that.