I don't believe so, at least I have never seen a production with a chorus nor have I read a version with one. I did, however, see a middle-school production where a few parts were added to get a couple more kids in it. I think a few lines were redistributed to make it happen.

Actually, contrary to what edh915 expressed, I have seen it done (at the middle school level) with a small chorus, as well as a few additional "Peanuts" characters added, and it worked VERY well.  The chorus wasn't in all scenes, but some were enhanced (i.e. the baseball game scene, and the book report scene).  When it was one of the more intimate scenes (Schroeder and Lucy at the piano, or Lucy and Charley at the psychiatric help stand, etc.) the chorus was not on stage.  It was directed by a woman who really knew how to get the most from her kids, and the show was better than most high school shows and some community theatre productions I have seen.  I don't know if that's a GOOD thing or a BAD thing, but nevertheless... 

This is not the show to add a chorus in.  There's not enough opportunity, nor is it written for the addition so it ends up looking choppy.  I love the few characters, anyway.