I have this linked from Middle School Plans. In looking on Marvin Bartel's
site for Creativity links to add to the lesson, I came across this lesson on
Student Art Critique:
http://www.goshen.edu/art/ed/critique1.html This is good for class critiques
of student work. I imagine it could be geared down to elementary too.
It is linked from Middle School and High School Lesson Plans both.