It is good to get feed back on a piece of art work but...
At school pieces of art work shouldn't be graded/levelled
Yes but can you really learn art ? I believe that you can draw naturally or you can't. I don't think someone can just walk in and teach you art. It is good to get feed back on a piece of art work but not everyone wants it from an art teacher. Yes they may have an art degree but it doesn't mean they will mark it professionally. I think that art teachers will go on their personal opinion of the work rather than looking at the piece with an open mind. I think that mark schemes are completely wrong in art. There's no right or wrong answer in the subject. It's your interpretation.