I disagree a bit.
Of course you shouldn't brag about how much better it will be for the kids to be in WDW than in the classroom, but all of my aunts and my mother are teachers. They would like to know why a child is being removed, where they are going, and what educational experiences they can bring back to share.
I wouldn't send the huge letter (while nicely done, I would think only the very strict schools would need something like that), but my aunts, as well as all of my teachers in Green Bay (K-12) added on little extra assignments for trips.
When we went to DC, I had to take pictures of two of my favorite monuments/buildings, and explain the history. When we went to California, I had to do a report on Alcatraz Island and bring back photos to share with the class. And for every Disney trip (at least until high school), I had to do things like little albums, or mini-reports with pictures, or get sand from a beach, or find out little known facts. The teachers
would like to know where the kids are going; at least all the ones I had.
They also want the experience to be shared...a little kid goes on a trip, they want them to be able to share it. I remember 1st-5th grade being a myriad of kids coming back from The Grand Canyon, Yellowstone, Disney, Skiing, Europe, California/SanFrancisco, etc. They/we all did big presentations and I remember a lot. And that was....about 15 years ago!