Children's book that featured a board game that made you shrink

I would have read this about 1988 or so. It was, as I recall, a collection of short stories that featured the same character-a young boy. In one of them he gets a board game that he plays for a bit but is unable to finish. Because he was told to go backwards on his last move, he begins to slowly shrink. At school, he has to use the drinking fountain and gets in trouble for jumping to try and reach it. When asked why he's jumping, he replies he's shrinking but gets in trouble anyway. He eventually figures out it's because of the game and he makes his piece advance around the board several times and this allows him to become his proper size.

The book was illustrated.

Jumanji maybe?

No, it had a lot more text than that. And I do think there were multiple stories. It was in a more standard novel format.

The Shrinking of Treehorn?

The S of T certainly has the drinking fountain episode. The illustrations are by Edward Gorey. I think there was a sequel, perhaps two. Maybe you had a "complete Treehorn."

That's it! It was the Treehorn Trilogy! Thanks so much for this.

Touchstone add: Treehorn Trilogy