I pretty much agree with what everyone else has been saying. Look for something positive to say unless they are honestly looking for constructive criticism. Then, being a teacher too, I would sandwich that in between positive comments.
Heres how that works as a teacher.
" Johnny you have a wonderful imagination. I see though that you need to write neater and do a spell check on your paper next time. You know Johnny if you retype/rewrite this paper for me I would like to put this on the bulletin board so people can see how to use their imagination."
(cause you would be surprised at how many of the kids I work with are lacking in imagination. )