Dear Miss Snark,
My biggest accomplishment so far as a writer is having a very well respected children's book publisher (Arthur A. Levine) request my full ms. at a conference. I am currently revising the story using the suggestions he and his editorial assistant were kind enough to provide. While I realize this is not in any way a publishing credit, I wonder if it wouldn't be worth mentioning in an agent query. Is it something you would wish to know?
Not only is this not a publishing credit, it's a rejection.
You want to lead with your strengths.