Hi Victoria: I have a suggestion. Many instructors will use a rubric (table of categories) that allocates points based on the degree to which a student has met or not met certain criteria. A well constructed rubric would not need to evaluate the art itself, but would allow you to grade the assignment based upon points earned by predetermined characteristics you expect from the assignment. In this manner, all students are graded according to an "objective and consistent" measuring tool. Good luck! Regards, Barry