Christmas Star is Medal of Honor
My mother remembers reading this story in school, possibly a short story in an anthology. A small boy is on a train on Christmas Eve and asks his mother if Santa can find him. Some soldiers (this was set during WWII?) overhear and enlist the help of the train staff and other passengers to get a tree, ornaments, and presents. But they can’t find a star for the top of the train. An older man who has been grumpy/dismissive about the whole thing offers his medal of honor for the star. She has been looking for this story for many years now!