I teach 7-9 and I always use self-assessment rubrics. I also require them to
write a small paragraph on the back telling me why they deserve their grade. I
try to get them to use the art "lingo" that we've discussed in class as well.
I tell them it's their job to try and convince me.
I then grade them using the point system and also take into account their
writing. I find that more often than not my grade is fairly close to theirs
and usually within the same letter range. This percentage increases as my
quarter winds down.
So I think it really a good thing to do. I believe it shows many of them
right off the bat what you expect versus what they think and gives them a chance
to rise your level of expectation.