How do you assess student artwork?

I assess student artwork in two parts. Immediately after a project a rubric will be use to grade the technical and design aspects of the piece, in accordance to the students abilities. Another form of assessment will occur three times during the term. These three assessments will be summative to track the students growth through out the course. The initial assessment will be used for both my benefit as well as finding a baseline for the students skills. I will benefit from this assessment by learning the skills of each student and adapt my lessons to their skill level while still challenging them. The second and third assessment will act as bench marks to show a quantitative developmental change.