The main issue is not what scale to use, how often to report, how many grades to combine, or how to combine them. These secondary issues can be decided only after you answer the main questions: What meaning do we want our grades to convey? and Who is (are) the primary intended audience(s) for this message? (Susan M. Brookhart on grades at Educational Leadership)
What do grades mean? What should they mean? To read Brookhart's piece, click the above hyperlinked text.