I was just given an opportunity to study under a respected writer in a well established novel writing workshop wherein several of the current members have had previous novels of theirs published. Not to sound too calculating here, but exclusive of the obvious benefits of a reputable writing group for an unpublished writer, would this be something worth mentioning in a query letter?
The only thing I care about is whether you can write. Plenty of nitwits have studied with fine writers, much like plenty of whack jobs read the New York Times.
IF however, your respected writer reads your novel, and says "this is hot spit" THEN you get to mention it to me. You might consider getting it in writing too. The way things are going I only believe what I can see and verify.